the use of criteria based dispatch 08 2001
TRANSCRIPT
THE USE OF CRITERIA BASED DISPATCH
IN THE PRIORITISATION OF 999 EMERGENCY
AMBULANCE CALLS
by
Matthew William Cooke
A thesis submitted to
The University of Birmingham
for the degree of
DOCTOR OF PHILOSOPHY
DEPARTMENT OF PRIMARY CARE & GENERAL PRACTICE
FACULTY OF MEDICINE THE UNIVERSITY OF BIRMINGHAM
AUGUST 2001
ii
Abstract
Criteria Based Dispatch (CBD) is one system used for prioritising 999 emergency
ambulance calls. The aim of prioritisation is to deliver a more appropriate and rapid
response to those with the most urgent needs.
This study aims to assess the safety and effectiveness of CBD in the prioritisation of 999
emergency ambulance calls by detecting where it fails to meet its objectives and to
inform wider plans for prioritisation in emergency care in the NHS.
The study consists of many components. These include studies of
• the opinion of experts on the present coding
• the present literature
• clinical state, interventions and outcomes in relation to prioritisation
• critically ill patients
• subsidiary studies that look at whether CBD performed well in a period of work
overload, the communication problems in 999 calls and a study of those who
were not transported to hospital following a 999 call.
There is little information in the literature that is applicable to the UK emergency
ambulance service system. The studies in this thesis combine to conclude that there is at
least a 12.6% under-triage rate, which may mean that critically ill patients are not
receiving the fastest and most appropriate response. The use of a guideline system is
allowing the dispatchers to improve on the CBD system by use of experience and
knowledge. Key groups of critically ill patients, may be unrecognised in 20% of cases.
Those with decreased conscious level, those who are bleeding or have suffered fits
appear to be at increased risk of under-triage.
CBD does not appear to be used to full advantage by the ambulance service in this study
to deploy resources most effectively.
Review of the guidelines is suggested and recommendations are made for change.
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Dedication To Heather, Hannah and Jenny.
iv
Acknowledgements
The author would like to acknowledge all of the following for their help in the conduct of this research. I am grateful to all the members of the Emergency Medicine Research Group at the University of Birmingham. Teresa Allan, Richard Morrell, Steve Edwards, and particularly to Sue Wilson for her advice and supervision and Pam Bridge for her assistance throughout the project. West Midlands Ambulance Service
Barry Johns, Chief Executive Steve Elliker, Emergency Control Centre Manager All the staff of the Emergency Control Centre Pippa Chalker, IT Department Jeanette Gray, Henrietta Street Ambulance Station Essex Ambulance Service
Gron Roberts, Chief Executive Rick Davis City Hospital NHS Trust
Jayne Hipkiss, my secretary Joan Holford, A&E Reception Supervisor Reception and Nursing Staff in A&E Medical Records Department and Ward Staff Experts Mr. John Belstead, Mr. Geoffrey Bryant, M. Seaward-Brown, Dr. Timothy Coats, Dr. Rowley Cottingham, Dr. Gareth Davies, Mr. Peter Driscoll, Dr. Richard Fairhurst, Dr. Brenda Fleming, Dr. Graham Gardiner, Dr. Robin Glover, Mr. Paul Grout, Dr. Henry Guly, Mr. Ian Harvey, Major Tim Hodgetts, Dr. Graham Johnson, Dr. Danny MacGeehan, Mr. Kevin Mackway-Jones, Mr. Richard Morrell, Dr. Adrian Noon, Dr. David Parkin, Mr. Patrick Plunkett, Mr. Paul Pritty, Dr. John Ryan, Mr. Brendan Ryan, Dr. Ian Robertson-Steele, Mr. Howard Sheriff, Mr. David Small, Dr. Steve Southworth, Dr. Ian Stewart, Mr. Andrew Swain. I am grateful to Linda Culley (King County, Seattle), Prof. Jeremy Dale, Prof. Richard Hobbs and Prof. Richard Lilford for their constructive comments and Rachel Hewitson for her secretarial support.
v
Funding:
The NHS Executive (West Midlands) Research and Development Directorate funded
this project.
Ethical considerations:
This study was approved by the West Birmingham Local Research Ethics Committee.
vi
Table of contents
Table of contents vi List of figures viii List of tables ix List of abbreviations xi Glossary xii Use of terms relating to urgency of care xiii 1 Introduction 1 2 Aim and Objectives 5 2.1 Aim 5 2.2 Objectives 5 2.3 Methodological overview 6 3 Overview 9 3.1 999 call handling 9 3.2 Triage and prioritisation 11 4 CBD system 14 4.1 Criteria Based Dispatch 14 4.2 History of CBD. 19 4.3 Review of Expert Opinion Study as an example of a cause for concern.
22
5 A systematic review of the evidence on the use of priority dispatch of emergency ambulances.
41
6 Clinical outcome study 54 7 Study of hospital alerts 90 8 Other studies 102 8.1 Study of changes in CBD when introduced to the UK 102 8.2 Patients not transported from the scene 108 8.3 Are 999 callers in a position to give triage information and receive first aid advice?
119
8.4 CBD usage at a time of exceptional workload 127 9 Conclusions 134 10 Papers published in relation to this thesis 141
vii
Appendices 1. The CBD(UK) coding system 143 2. Objectives of CBD and dispatch categories 156 3. Sample of recruitment letter 157 4. Guidance for Study α & β 158 5. Instructions for study δ . 159 6. Other sources of publications used in the literature search. 160 7. Proforma for articles undergoing expert appraisal in the Literature Review.
161
8. Articles undergoing expert appraisal in the Literature Review. 163 9. Data collection Proforma 165 10. Recommendations for modifications to CBD 166 References 169
viii
List of Figures
Figure Title Page Figure 1.1. Trends in the number of emergency 999 ambulance calls and
patient journeys provided by NHS ambulance services 1976-1999.
2
Figure 3.1. Handling of 999 calls. 10 Figure 4.3.1. Summary of changes by panel suggested by 50% or more of the
experts in any panel - letters represent panel of experts not CBD codes.
35
Figure 6.1. Triage Nurse ambulance prioritisation assessment form. 57 Figure 6.2. Time of 999 call vs. CBD category. 66 Figure 6.3. Percentage of calls classified as category “A” per hour. 66 Figure 8.2.1. Variation of non-transported 999 calls with day of week. 111
Figure 8.2.2. Variation of non-transported 999 calls with time of day. 112
Figure 8.2.3. Non transport by CBD code. 112
Figure 8.2.4. Total cases not transported. 113
Figure 8.2.5. Reasons for not requiring transport. 114
Figure 8.2.6. Cases dealt with by another agency. 114
Figure 8.3.1. Who calls for the emergency ambulance? 123
Figure 8.4.1. Hourly 999 call rate compared to a control time period. 129
ix
List of Tables
Table Title Page Table 3.1. Triage category of 999 ambulance cases compared to all A&E
attenders at City Hospital, Birmingham in March and April 1998. 12
Table 4.1.1. Emergency calls: response times for services wit hout call
prioritisation, by Ambulance Service, 1998-99.
17
Table 4.1.2. Emergency calls: response times for services with call prioritisation, by ambulance service, 1998-99.
18
Table 4.3.1. Example of randomised CBD list as provided for panel β. 24 Table 4.3.2 Example of CBD list (in CBD code book order) as provided for
panel δ 25
Table 4.3.3. Participation and response rates. 26 Table 4.3.4. Expert agreement by CBD category. 26 Table 4.3.5 All changes proposed by expert panel 27 Table 4.3.6. Cases where 50% or more of experts in all panels suggested
change. 36
Table 4.3.7. Disagreements by 50% or more of experts on a panel for categories involving children under five.
36
Table 4.3.8. Changes induced if decision of each 50% or more of experts on a panel were used.
37
Table 5.1. Search strategy for electronic databases 42 Table 5.2. Classification of all articles identified. 45 Table 5.3. Summary of results of literature search by database. 46 Table 5.4. Papers relating to priority dispatch of ambulances and containing
original data. 48
Table 6.1. Categories used by experts to define urgency. 59 Table 6.2. Codes for justification of urgency of care. 59 Table 6.3. Sources of data for outcome study. 64 Table 6.4. Distribution of study patients by CBD category. 64 Table 6.5. CBD coding by sex of patient. 65 Table 6.6. Variation of category distribution by age groups. 65 Table 6.7. A&E diagnosis of cases in the study. 67 Table 6.8. Internal consistency of experts. 69 Table 6.9. Analysis of Coding by Dispatchers and Experts. 71 Table 6.10. Error rates of CBD 72 Table 6.11. Interventions in relation to CBD status 74 Table 6.12. Physiological status in relation to CBD code. 75 Table 6.13. Discharge from A&E in relation to CBD code. 76 Table 6.14. Admission to hospital in relation to CBD code. 76
x
Table Title Page Table 6.15. Admission to Coronary care or High dependency in relation to
CBD code. 72
Table 6.16. Admission to Intensive Care unit in relation to CBD code. A ITU admissions direct from A&E B all ITU admissions, including admissions subsequent to A&E
78
Table 6.17. Deaths in relation to CBD code. A Deaths before arrival at or in A&E B Deaths after leaving A&E during hospital stay
79
Table 6.18. Duration of complaint in relation to CBD code. 80 Table 6.19. Response times by CBD category.
A response times by CBD B percentage achieving new 2001 standards
81
Table 7.1. Information from ambulance database for alerts study 92 Table7.2. Criteria for determining critical illness on clinical grounds 92 Table 7.3. Distribution of diagnoses by the alerting ambulance crew and the
dispatcher’s CBD classification. 93
Table 7.4. Comparison of dispatcher and ambulance crew diagnosis. 94 Table 7.5. Conscious level on AVPU scale vs. CBD category. 96 Table 7.6. The Revised Trauma Scores (RTS) for trauma patients. 97 Table 7.7. Glasgow Coma Scale of trauma patients. 97 Table 8.1.1. The changes in coding of CBD when imported into UK. 103 Table 8.1.2. Decreased conscious level coding in UK and US. 106 Table 8.1.3. Variation in bleeding code according to presenting complaint. 107 Table 8.2.1. Coding of reason for non-removal. 110 Table 8.3.1. Search strategy on communications difficulties in 999 ambulance
calls. 119
Table 8.3.2. Communication Difficulties 122
Table 8.3.3. Location of person making emergency 999 call 122
Table 8.4.1. Emergency ambulance calls by prioritisation category for New
Year’s Eve and a control period.
130
Table 8.4.2. Percentage of calls responded within 8 and 14 minutes. 130
Table 8.4.3. Average response times and the range of response times by
category.
131
xi
List of abbreviations
A&E Accident and Emergency AED Accident and Emergency department ALS Advanced Life Support ANOVA Analysis of Variance ATLS Advanced Trauma Life Support AVPU Alert-Voice-Pain-Unresponsive scale of unconsciousness BASICS British Association for Immediate Care BIDS Bath Information Database Service BLS Basic Life Support BP Blood Pressure CBD Criteria Based Dispatch CBD(UK) Criteria Based Dispatch, UK version CINAHL Cumulated Index of Nursing and Allied Health
Literature CPR Cardio-pulmonary resuscitation CVA Cerebro-vascular accident EMD Emergency medical dispatcher EMS Emergency medical services EMT Emergency medical technician GCS Glasgow Coma Score GP General Practitioner ITU Intensive Therapy Unit MI Myocardial infarction ORCON standards National standards for ambulance response times.
Operational Research Consultants in Health standards PHC Prehospital care QS Quality Score RR Respiratory Rate RTA Road traffic accident RTS Revised Trauma Score SI Shock Index WMAS West Midlands Ambulance Service NHS Trust
xii
GLOSSARY
112 The pan European emergency ambulance access number
911 The emergency access telephone number used in many
parts of America
999 The emergency services telephone access number in the
UK
Alert The process of an ambulance service informing a
hospital (alerting them) of the imminent arrival of a
seriously ill patient
Call taker The person in the ambulance control room who initially
receives the 999 call and takes details from the caller
Control Assistant Person working in ambulance control room ( one of the
tasks they undertake is to be a call taker)
Dispatcher The person in the ambulance control room who is
responsible for mobilising the ambulance. Also used to
refer to anyone working in the control room in the
dispatch process.
Over-triage Where an individual records a triage cate gory higher
than the relevant expert.
Pre-arrival instructions Instructions given to caller over the telephone after the
dispatch of ambulance but prior to it arrival
Response time The time from receiving the 999 call in ambulance
control to arrival of ambulance personnel next to the
patient.
Under-triage Where an individual records a triage category lower than
the relevant expert.
xiii
Use of terms relating to urgency of care.
The Oxford English dictionary (OED) 1 does not differentiate any priority between the
words immediate, emergency and urgent. The OED definitions are:
Immediate occurring or done at once or without delay
Emergency a medical condition requiring immediate treatment
Urgent requiring immediate action or attention
Within the ambulance and emergency services, a different interpretation is used,
although it has never been formally defined. In this thesis the terms are used as follows:
Immediate without any delay
Emergency with minimal delay (for example, a few minutes)
Urgent with only a small delay
For example, an urgent ambulance is often requested to arrive within 15 minutes to 2
hours, whereas an emergency ambulance aims to attend within a maximum of 14-16
minutes. If care is needed immediately, this implies that deterioration in the patient's
condition will occur from that time or may already be occurring.
1
1. INTRODUCTION
The statutory ambulance services in the United Kingdom have responsibility for the
provision of the 999 service relating to healthcare2. As such they provide prehospital
care and transport of medical emergencies following a 999 emergency ambulance call.
They are also responsible for the transport of a patient to hospital following the request
of a general practitioner. The ambulance services also have responsibilities relating to
emergency planning and major incidents.
The provision of transport between hospitals and to non-urgent healthcare is undertaken
by both private and statutory ambulance services. There were 1.1 million urgent GP
cases transported in 1997-98. These utilise the same resources as 999 calls. The GP
urgent calls are not currently prioritised by ambulance control and do not therefore form
part of this study. At present 999 ambulance calls receive priority over a GP call unless
the general practitioner states that the case needs an “immediate” ambulance. This study
is only concerned with the provision of the emergency 999 service by the ambulance
service.
Ambulance services are experiencing a rapidly increasing demand. The number of
emergency ambulance journeys reported in 1997-8 was 2.7 million in England. These
resulted from 3.6 million ambulance calls, a rise from 3.33 million emergency
ambulance calls in 1996-973. The trends since 1976 are demonstrated in Figure 1.1.
These figures represent an ambulance call rate of 123 calls per 100,000 population per
week in England (92 ambulance journeys /100,000 /week as there is an average of 0.75
journeys per call3). In a study of 25 mid-sized US cities , an ambulance call rate of 158
per 100,000 population per day4 was calculated. A wide variation of call rates has been
noted in Europe 5.
2
Figure 1.1. Trends in the number of emergency 999 ambulance calls and patient
journeys provided by NHS ambulance services 1976-1999.
The severity of illness experienced by those for whom a 999 emergency ambulance call
is made varies widely. When the hospital care given to those transported to hospital is
taken into account, nearly half may be considered retrospectively not to have required an
emergency ambulance. In a review of the international literature, it was demonstrated
that, despite a wide range of methodologies being used to estimate appropriateness of
use of ambulances, there was surprisingly little variation in the estimates of “misuse” 6.
In nine of the ten studies for emergency ambulances, a figure between 30% and 52% of
inappropriate use was reported6. Inappropriate was defined in these studies as not
requiring an ambulance because of medical need. However, inappropriate, as defined by
medical condition, does not necessarily signify misuse. There may be social reasons why
a person cannot obtain transport to hospital (for example, an elderly lady living alone in
a violent area) where an ambulance is the only source of transport. The UK system does
not have any provision for transport without EMT or paramedic care. Many studies
actually assess whether the call was appropriate for paramedic care rather than for
ambulance service attendance.
In Birmingham, in 1980, 51.7% of all calls (42.6% of medical and 63.2% of trauma
cases) were deemed to be unnecessary7. At least 23.4% of patients needing emergency
care (within 10 minutes of arrival in hospital), arrive by means other than emergency
ambulance 8. These cases represent those who would be appropriate for 999 ambulance
3
care but decide to use another means of transport to hospital. Improvements in the
emergency care system, such as increased usage of NHS Direct and better educational
strategies, may encourage these non-ambulance users to utilise the emergency service as
well as encouraging inappropriate users not to use an ambulance.
The problem of ambulance misuse is international. In Stockholm, 50% of ambulance
cases were reported as low priority following medical assessment by phone and 22%
resulted in no patient transport9. In Australia, 23% of calls resulted in no transport and
20% were non urgent10. In Taiwan11, 31.7% of calls did not trans port a patient and of
those transported, 27.6% did not require even basic EMT care. However, in this study
the majority of critically ill (86%) did not arrive by ambulance. In Canada, an
inappropriate call rate of 49% has been described12.
In a situation where some consider there is inappropriate use of the emergency service, a
system is needed that can offer an alternative service to the “abusers” of the system if
emergency ambulance services are to provide a better service to those in true need of
medical assistance. There is no work explaining why people call an ambulance when
there is no urgent medical need. Inappropriate provision by other services may be the
cause.
The reasons may include:
• A perception of urgency because of lack of medical knowledge
• Inability to contact other sources of health care
• Non-availability of other transport
• Poor comprehension of the role of the ambulance service.
Those not requiring an emergency ambulance may require:
• A non-emergency ambulance service
• Taxi-type transport to hospital
• Medical care at home
• Advice only
• Care from other health care providers
• Non medical attention, for example, social services.
4
NHS Direct is a telephone advice line being developed in the UK to work in parallel
with the 999 service13. It aims to provide advice on urgent and routine medical problems.
One of the aims of the service is to direct people to the most appropriate source of
healthcare and to an appropriate route of entry into the health care system. The
introduction of this advice line may increase or decrease the ambulance service
workload. Present work shows that it has had little impact on ambulance service or A&E
department workload14.
The increasing demands on ambulance services and the limited resources available
suggest that the most cost effective means of providing the service is to prioritise calls
(give priority to those cases needing urgent paramedic care or urgent transport to
hospital).
Referring the “abusers” to an alternative service or putting them in a queue behind more
urgent cases relies on the ability of the system to prospectively and accurately select that
group of callers. An inability to detect emergency cases could result in a fatal delay in
medical care. The safety of prioritisation and triage systems in prehospital care in the
UK has not been assessed. This study aims to assess one of the systems for prioritising
999 emergency ambulance calls that is currently in use in this country.
5
2 AIM AND OBJECTIVES
2.1 Aim: To assess the safety and effectiveness of Criteria Based Dispatch (CBD) in the
prioritisation of 999 calls.
2.2 Objectives
• To critically review existing literature relating to prioritisation of emergency
ambulance calls
• To relate prioritisation levels determined by CBD with clinical findings,
interventions and outcome
• To determine the frequency of under-triage of 999 calls, in the light of a medical
opinion
• To identify enhancements to the existing system which will minimise the extent of
under-triage
• To compare expert medical opinion following case review with the
prioritisation by CBD
• To study the incidence of critically ill people who are under-triaged by CBD.
• To identify enhancements to the existing system which may improve the accuracy of
CBD
• To compare the triage of 999 ambulance calls by CBD with other nationally
accepted triage systems and guidelines.
Parallel studies contributing to this thesis aim:
• To study the use of CBD for patients who subsequently do not use an
ambulance for transportation to hospital
• To study the communication difficulties which may affect information
gathering and have implications on the effectiveness of CBD
• To study the impact of CBD on ambulance dispatch at times of maximal
demand.
6
2.3 METHODOLOGICAL OVERVIEW
Initially the CBD system is described to ensure the reader understands the system that is
being studied. The way in which it was introduced in to the UK is important as a
possible cause of changes in the safety and effectiveness of the system.
The author was aware of anecdotal comments that the coding system did not achieve a
safe system of coding. When introduced, comments suggested that CBD did not have the
support of experts in the field. The expert opinion study was undertaken to determine
whether the system coincided with the thoughts of experts and therefore whether the
allegations of an unsafe system may be true (see chapter 4). The evidence base of the
system was also assessed to determine whether the system was based on evidence and
whether CBD had undergone the scrutiny of primary research (see chapter 5).
Most work in monitoring effectiveness of emergency medical dispatch looks at quality
assurance (namely, adherence to the system, rather than clinical effectiveness)15. Where
clinical care has been assessed, work relates only to the prehospital element of care16.
Only by studying the complete pathway through the accident and emergency department
to definitive diagnosis can all those in need of emergency care, whether prehospital or in
hospital, be determined.
A clinical outcome study was undertaken to determine the safety and effectiveness of the
system (see chapter 6). There is no absolute gold standard against which to measure a
prioritisation system. For absolute safety, it should detect all those who could possibly
deteriorate if an ambulance response is delayed. To be an effective resource
management tool it should optimise use of resources and therefore minimise the number
of high priority calls, allowing a lesser response to those who are not needing emergency
care by an ambulance crew. This thesis relie s on the premise that in general, those who
are at risk of death or serious illness should expect to receive the most urgent treatment.
It also relies on the presumption that those with serious illness or injury will benefit from
earlier attendance of an emergency ambulance. This has been validated for cardiac arrest
and a few other conditions17,18,19 but is an assumption for most conditions since it is not
ethical to test the hypothesis by delaying care to the potentially critically ill patient.
7
Mortality and morbidity are important outcome measures in medical research. However
a study of medical dispatch cannot rely solely on these parameters because of the small
number of deaths. Dispatch is only one component in a chain of events, from the initial
symptoms to eventual outcome, of an emergency situation. It is necessary in many
instances to use surrogate outcome measures to evaluate a dispatch centre and the
following have been recommended20:
• Appropriate use of ALS units
• Prioritisation of calls
• Accuracy of referral to GPs
• Information gathering during telephone call
• Duration of call
• Adherence to guidelines.
This study looks at the first two of the above, which are the clinically relevant items to
the United Kingdom system and looks at the difficulties of information gathering in
regard to telephone calls (see chapter 8.3). For that reason, the need for an urgent
response was assessed in three ways. Firstly, expert opinion was obtained, secondly
clinical indicators were utilised and thirdly outcomes were assesse d. Proxy measures of
outcome have to be used, such as length of stay in hospital and admission in conjunction
with peer review. The outcome study of this thesis uses measures such as the need for
prehospital intervention, physiological parameters and condition on arrival in the
accident and emergency department as indicators of need for emergency care. The use of
experts remains important for those cases where there is no validated system of
determining the urgency of need for an ambulance.
The study of the critically ill focuses on those with life-threatening conditions at the time
of their arrival in hospital (see chapter 7). Other studies have looked at the global picture
or specific diagnostic groups as demonstrated in the literature review in this thesis. With
the great majority of patients not requiring intervention, a study that only looks at the
whole population (in this case all those who call 999) produces a percentage undertriage
rate that may appear very low. But when the numerically small group who could benefit
most from a dispatch prioritisation system are studied, the safety of the system can be
more effectively analysed. Clinically, the most important safety feature of CBD is its
8
ability to detect the seriously ill who may benefit from more rapid care. In an additional
study, this sub-group were studied to determine if CBD was detecting patients who
arrived at hospital in a serious condition. Detection of those with serious illness is not a
simple matter. In certain conditions such as trauma, there are validated scoring and
evaluation systems, which allows confirmation of the severity of the patient’s
condition21. These are, however, designed for analysis of patient groups rather than
individual patients. Peer review is equally effective as scoring systems in assessing
quality of trauma care22, but they are not available for most medical conditions.
If this system is not working perfectly, then it is important to determine why. The study
of changes that were made to CBD when it was introduced into the UK (Chapter 8.1) is
designed to determine whether any of the subsequent problems were caused by these
changes. The problems may be related to an inability to obtain information of a
sufficient degree of accuracy over the telephone to enable accurate prioritisation. The
study of communication difficulties is designed to explore this possibility (Chapter 8.3).
It has been proposed that CBD has other uses as well as the ability to detect those in
need of more urgent care. It has been suggested that those in the lowest prioritisation
category (category “C” patients) may not need an ambulance response. Referral to
General Practitioners is not undertaken at present direct from the 999 call in the UK,
although it has been proposed. This group is analysed in this study to determine whether
they could be safely allocated to other care providers. A study of ambulance cases where
a patient was not transported is designed to demonstrate whether CBD is effective at
detecting this group (see chapter 8.2).
CBD is also designed to help resource allocation, so that those with the most urgent need
get an ambulance in preference to those with less urgent needs. A study of the busiest
period of the year, New Year’s Eve, determines whether CBD is used as a means of
allocating resources that are limited compared to requirements (see chapter 8.4).
By combining these studies, this thesis obtains a wide picture of the safety and
effectiveness of CBD in prioritising emergency ambulance calls, assessed in a variety of
ways.
9
3. OVERVIEW
3.1. 999 call handling
When a caller makes a 999 call they are initially connected to the telephone company
operator, who confirms the number they are calling from and determines which of the
emergency services they require. The telephone company operator then connects to the
ambulance service, if appropriate, and informs the ambulance service call taker of the
phone number of origin. The call taker can check this against the automated call
tracking. (This process is summarised in Figure 3.1)
The call taker then obtains the identity of the caller, the location at which the ambulance
is required and the main medical problem. This information is then transferred to the
dispatcher. The dispatcher then decides on which ambulance to send to this case. The
dispatcher’s computer gives details of all the ambulances available and their estimated
travelling time to the incident, aided by automated satellite vehicle tracking.
Whilst the ambulance is being dispatched, the call taker undertakes the questioning
needed for the Criteria Based Dispatch prioritisation (see chapter 3.2), as well as
obtaining other necessary information. This information may include more detail on
access (for example, a neighbour has the key) or of other services required (for example,
police or fire). These additional details are then passed to the dispatcher who can modify
the ambulance response and also inform the responding crew.
The call taker then offers to give first aid advice to the caller whilst the ambulance is
responding. If necessary, they stay on the line until the ambulance crew arrives.
If the call has been made from outside the area or via a mobile phone or the location was
not known to be in the West Midlands, then the telephone company may initially direct
the call to another ambulance service. That ambulance service will then pass on details
to the host ambulance service. The ambulance service receiving the call may not
undertake prioritisation of calls and there may therefore be inadequate information to
categorise the call.
10
999 callerMobile or
Outside West Midlands
Other Ambulance control
Accident and Emergency departmentNurse Triage
Ambulance CrewAlert hospital if critical cases
Ambulance CrewArrive at scene
Treat patient, move to ambulanceMobile to hospital
Ambulance CrewMobile on case
DispatcherReceives CBD Priority codeUpdates ambulance crew
Sends additional resources if required
DispatcherAllocates Ambulance to case
Call takerGives First Aid advice
Call takerDetermines CBD Priority code
Dispatcher informed
West Midlands Ambulance Emergency Control Centre (ECC)Call taker
Entry on ECC computerised dispatch system
Telephone Company Operator
999 callerLand line
West Midlands
Figure 3.1 Handling of 999 calls.
11
3.2. Triage and prioritisation
Any system with limited resources or unpredictable requirements needs to be able to
control its response and balance need with demand. Until 1997, the 999 ambulance
service in the UK worked on a “first come, first served” basis. Someone calling 999 for a
sprained ankle that had occurred one week ago had priority over a call thirty seconds
later from a person with severe chest pains similar to their previous myocardial
infarction. The level of demand for ambulances fluctuates by day of the week (for
example, Monday is invariably the busiest day of the week) and time of the day (with
peaks at lunchtime and in the evening) 23,24. The simultaneous need for several
ambulances may lead to a relative lack of resources. A system which can give priority to
those with life threatening problems is required, if available resources are to be used
most effectively and safely. Such a system must be proven to be safe , reliable and
effective in all situations and settings.
Triage is used in all the accident and emergency departments in the UK. It is a system of
assessment that is attributed to Baron Dominique Jean Larrey, who developed the
principle of sorting casualt ies for treatment during the Napoleonic wars25. The practice
of triage has been adopted in A&E departments to ensure that patients with potential
critical illness do not wait unnecessarily for assessment and treatment2. However,
performance tables based on time before triage have been demonstrated to have no
correlation with quality of care26. This may be due to others waiting for triage or because
of the failure to develop a system of decision making that rapidly and sensitively detects
the most ill. The value of triage has been questioned, and its reliability is in doubt. The
decisions for assessment made by doctors, nurses or computer systems are not
reproducible on retrospective examination 27. The Manchester triage system (MTS) of
triage was introduced in 199628. It uses a series of flow charts for various "presentations"
with key " discriminators" to determine the triage category. A multidisciplinary
consensus group developed these guidelines. The system has been adopted widely
throughout the United Kingdom. There is only one published study suggesting that it is a
sensitive tool for detecting the critically ill8.
The majority of A&E attenders do not need emergency care (within 10 minutes of
arrival). The urgency of cases at City Hospital, Birmingham in March/April 1998 is
12
shown in Table 3.1. Triage scale 4 or 5 (could wait two hours or more for treatment)
was allocated to 34.9% of ambulance cases and a further 46.1% were triage category 3
(could wait one hour for treatment) 29,30.
Table 3.1 Triage category of 999 ambulance cases compared to all A&E attenders at
City Hospital, Birmingham in March and April 1998.
Triage category
1
2
3
4
5
Not Specified
Grand Total
Target time to be seen in AED
0 mins 10 mins 60 mins 120 min 240 mins
Ambulance 101
4.4%
330
14.3%
1066
46.1%
780
33.8%
25
1.1%
8
0.3%
2310
100.0%
All cases 172
1.7%
713
7.1%
3448
34.2%
5069
50.3%
390
3.9%
287
2.8%
10079
100.0%
Triage is also needed for emergency ambulance cases. The potential problems in
undertaking the triage of a 999 call are even greater than those experienced in the
accident and emergency department. These difficulties relate to several factors
including:
• Inability of ambulance service call taker to visualise the patient
• Anxiety of the caller
• Language difficulty
• Anxiety that triage is delaying the arrival of the ambulance
• Caller may not be with the patient or not have full details
• The training of the person answering a 999 call compared to A&E nurses
• The caller’s lack of medical knowledge.
These potential problems must be weighed against the potential advantages of an
ambulance triage and dispatch system, which include:
• Improved response times for critical cases
13
• Matching skill level to incident requirement (for example, determining whether
an ambulance technician or paramedic or a doctor is required)
• Opportunity to give advice over the telephone before the arrival of the
ambulance.
There are also potential secondary benefits from 999 call prioritisation, which relate to
utilising a category that allows a delayed or less urgent response. These include:
• Lower accident rate of ambulances responding to 999 calls because of less
urgent response driving
• Better resource alloc ation
• Improved cost effectiveness.
If a category can be defined that is not an emergency or does not require medical
assistance, it is possible that these could be diverted to another agency, or be delayed.
Mistriage in this situation could have severe consequences, as it removes emergency
medical care rather than simply delaying the arrival of the ambulance.
As with any triage or prioritisation system, it is likely that call prioritisation will produce
the greatest change in a system that is resource limited. It is unlikely that an ambulance
service with ambulances always available and with a highly trained paramedic on each
vehicle will gain markedly more from an ambulance dispatch system than could be
achieved with pre-arrival advice alone.
14
4. EXPLANATION OF CBD SYSTEM
There are two main types of ambulance dispatch system presently in use in the United
Kingdom for prioritising 999 calls. The first is driven by strict protocol with mandatory
questions and predetermined actions. An example of this is A dvanced Medical Priority
Dispatch 31 (AMPDS). The second type is based on guidelines and Criteria Based
Dispatch 31(CBD) is of this type.
4.1 Criteria Based Dispatch
By asking a series of key questions, the ambulance service control assistant prioritises
the call and assigns the patient to a CBD category. The dispatcher first determines the
chief complaint and moves to the flip chart for that condition. By asking a series of
questions the dispatcher can allocate a specific category from the chart.
This category is denoted by a code with three components:
• The first number signifies the chief complaint
• The second component is the letter defining the prioritisation category
• The third component is a numerical code for the specific symptom or
circumstances.
For example, code 7A2 signifies:
• Chief complaint is chest pain (coded 7)
• Prioritisation is category “A”
• Symptom is “short of breath, unable to talk” coded 2
A full listing of the codes is contained in Appendix One.
The prioritisation categories, as defined by the originators of CBD in King County, are:
• Category “A” An immediate life-threatening situation requiring urgent
assistance. The objective is to provide immediate aid by
telephone advice followed by rapid on scene assistance.
15
• Category “B” A serious condition that is not immediately life-threatening.
The objective is to provide intervention as soon as possible.
• Category “C” Other non-serious or non-life-threatening conditions that
requires conveyance to hospital.
It has been stated that the advantage of a guideline system, such as CBD, is the freedom
given to the person taking the call32. The initial information given by a caller may
obviate the need for some questions; for example, there is no need to ask about
conscious level if the caller is the patient. Nicholl31 demonstrated that in 50% of cases,
the mandatory question about presence of breathing was not asked. Critics would say
that this was an omission, protagonists would say that in the other half, it was apparent
and did not need to be asked. CBD allows the control assistant to stop questioning as
soon as a high priority response is realised. There is no need to ask any further questions
about the patient who is unconscious before deciding a priority. An ambulance is
required, although more information may then be subsequently gathered to inform the
responders of more details, and to allow more accurate pre-arrival instructions to be
given The advantage of a protocol system is stated to be that it does not rely on the
“exercise of good medical judgement” and is more amenable to quality assurance32.
There have been no comparative studies of the two systems. Much of the literature
appears to be clouded by commercial interest having been written by the originators of
the systems 33, 34 35, 36, 37, 38, 39, 40, 41 rather than as a result of independent scientific
appraisal.
In America, the categorisation determines the level of response, that is whether a
paramedic or technician is responded. In the UK, it is used to determine the time, not the
level of response. The system aims to ensure that time critical illness and injury are
attended by an appropriately trained carer within a set time. In the West Midlands,
resources other than an ambulance may be used to ensure rapid response to a category
“A” incident. These include ambulance personnel on motorcycles or in cars, acting as
first responders, with an ambulance responding later if necessary. In other areas of the
country, non-ambulance personnel may be used for this role, including local doctors,
police and firefighters (personal communication, Ambulance Service Association).
16
The Department of Health’s review of ambulanc e performance standards (ORCON)42
has proposed the following response time standards for urban ambulance services, such
as West Midlands Ambulance Service.
• Category “A” 75% of calls within 8 minutes
• Category “B” 95% of calls within 14 minutes
• Category “C” Currently using the same standards as B
and the following response time standards for rural ambulance services
• Category “A” 75% of calls within 8 minutes
• Category “B” 95% of calls within 19 minutes
• Category “C” At present using the same standards as B
The performance against these standards is documented in Figures 4.1.1 and 4.1.2
The future role of Category “C” is still being debated. The group should contain those
with non-serious or non-life threatening conditions that still require conveyance to
hospital. It does however contain several sub-groups including:
• Those who need minor medical care
• Those who need non-medical assistance
• Those who simply need transport
• Those who do not need to attend hospital, because the condition has resolved or
is minor
• Hoax and inappropriate ambulance calls
• A proportion who have been mistriaged and who need emergency care.
Before a decision is made on how to manage these cases, it must be shown that this
category includes the minimum number with serious illness and that the sub-groups can
be identified. An informed risk assessment must be made, knowing the level of error and
the possible consequences.
The work included in this document is the first study of the UK modification of CBD in
operation.
17
Table 4.1.1. Emergency calls: response times for services without call prioritisation,
by Ambulance Service, 1998-99.
Ambulance Service Total number Response Response within of emergency within 8 19 minutes
(Rural) calls resulting in minutes 14 minutes
(Urban) ambulance
arriving (%) (%)
at scene of incident
(thousands) Rural Services
Durham County 36.8 38.1 93.5 Humberside 37.5 58.2 97.3 North Yorkshire 35.8 55.4 95.3 Lincolnshire Ambulance 52.6 57.9 95.0 Nottinghamshire 76.2 55.6 96.4 East Anglian 100.7 41.5 90.2 Bedfordshire & Hertfordshire 90.2 51.3 95.6 Kent 86.3 41.7 93.2 Hampshire 77.1 52.8 96.1 Wiltshire 22.8 51.9 94.5 Isle of Wight 6.4 47.0 95.8 Oxfordshire 24.7 53.1 94.5 Gloucestershire 24.3 50.9 95.0 Hereford & Worcest er 30.4 52.1 96.4 Shropshire 20.7 54.6 95.6 Urban Services West Yorkshire. 155.8 59.0 94.9 South Yorkshire 82.4 41.3 90.7 Surrey. 70.7 61.1 94.6 London Ambulance Service 685.0 38.7 86.9 Avon Ambulance Service 54.0 53.5 92.2 Greater Manchester 221.8 63.7 94.9
18
Table 4.1.2. Emergency calls: response times for services with call prioritisation, by Ambulance Service, 1998-99.
Category “A” calls Category “B” calls
Ambulance Service
Response Response
Total number
of emergency
calls resulting in response / ambulance arriving at scene of incident
(thousands)
Total number of emergency calls resulting
in response/
ambulance arriving at scene of incident
(thousands)
within 8
mins (%)
within 19 minutes
(Rural) or 14
minutes (Urban)
(%)
within 8 minutes
(%)
Within 19
minutes (Rural) or
14 minutes (Urban)
(%) Rural Services
Cumbria 3.5 59.6 93.7 17.7 59.1 93.5 Northumbria 20.3 57.1 97.8 83.0 52.7 96.5 Derbyshire 14.7 33.3 82.9 37.9 25.5 81.2 Leicestershire 11.0 42.9 89.1 42.6 36.3 88.3 Essex 21.1 61.9 97.7 84.7 56.5 96.8 Sussex 24.8 58.8 98.8 77.9 52.9 95.1 Dorset 22.2 60.3 96.8 25.2 59.3 97.4 Royal Berkshire 5.8 58.1 97.6 37.6 40.9 94.8 The Two Shires 15.0 61.2 97.9 44.2 60.1 97.6 West Country 22.9 41.7 90.0 79.7 40.7 89.6 Staffordshire 19.4 91.2 98.3 35.8 81.8 97.1 Warwickshire 3.6 63.2 97.3 21.0 49.9 94.8 Lancashire 24.9 68.5 98.3 75.6 63.6 97.3
Urban Services Cleveland 10.9 61.5 94.0 21.9 63.6 93.9 West Midlands 54.2 68.0 96.2 134.7 58.9 94.4 Mersey 80.2 56.9 94.2 104.7 54.0 93.4
19
4.2. History of CBD.
The Criteria Based Dispatch system was developed and is licensed by King County
Emergency Medical Services in Seattle, Washington, USA. The history of its
development in the USA has already been documented16. The Association of Chief
Ambulance Officers undertook the modification of CBD for use by ambulance services
in the UK. In 1992, Essex Ambulance Service undertook some work relating to
prioritisation of 999 calls, resulting in the “Anglicisation” of the system in 1993. This
was primarily a translation of the terminology from American to English. However, the
UK Resuscitation guidelines on cardiopulmonary and choking replaced those of the
American Heart Association. (personal communication, R Lane)
This system was then submitted to the Joint Royal Colleges Ambulance Liaison
Committee whose members unanimously agreed with the need for change and endorsed
the continuing need for national standards for “A”, “B” and “C” responses. They also
suggested:
• The need for local audit
• Need to consider total time to hospital as well as response time
• Need for better outcome measures to be developed and monitored
• Standards must be locally clinically acceptable
• Balance between first response vehicles and patient carrying ability
• Telephone advice encouraged
• Medical adviser should adjudicate uncertain Category “C” calls
• Need to define Category “C” before use
• Use CBD for doctor’s urgent calls after an education programme
Personal communication (Joint Royal Colleges Ambulance Liaison Committee)
Suggested modifications to coding included the following being promoted to Category
“A”:
• Acute hypovolaemia
• Documented hypotension
• Rhythm disturbances
• Some road traffic accidents.
20
In March 1994, Prof. Jon Nichol of the Medical Care Research Unit, University of
Sheffield studied CBD. These findings have been published as “The safety and
reliability of priority dispatch systems”31
His recommendations included:
• All head injuries should be high or medium response
• All children under five should be assigned to medium or high categories
• Training needs to ensure correct identification of the main complaint
• System should account for other circumstances than clinical state before assigning
low priority category
• Need to assess reliability of information obtained and if in doubt assign a higher
category
The above works contributed to the review of ambulance performance standards42. This
report identified five groups of patients who were considered to have “immediately life
threatening conditions”. Further consultation amongst ambulance services resulted in
two further groups being added when the final report was published.
The five original groups were:
• Chest pain associated with pallor, sweating, shortness of breath, nausea or
vomiting, but excluding those with pain intensified by breathing
• Individuals identified as unconscious, fitting or unresponsive for any cause
• Individuals with severe breathing problems who are unable to speak in whole
sentences
• Individuals who have suffered trauma with penetrating injuries to the head or
trunk
• Any individuals recognised as having anaphylactic shock
21
The subsequent two groups were:
• Children under two years of age
• Females suffering severe obstetric haemorrhage.
In December 1996, the NHS Executive circulated a list of dispatch codes to fall within
Category “A”42. From this list, the CBD system was realigned and the system evaluated
in this thesis was published - CBD (UK) March 1997 version. The overall changes are
outlined in section 8.1.
In only one case was the American code upgraded. In thirty-seven cases the clinical
condition had its priority downgraded. The exception to this is the new UK category for
“children under two years” who are all classified as an “A” response. Every instance of
“uncontrolled haemorrhage” except nosebleed is downgraded. Some anomalies were
created with the “bleeding” and “gynaecology” sections, which are discussed in chapter
8.1.
The system of CBD currently in use by ambulance services in the UK has been
developed from the American system calling upon some evidence but mostly based on
the opinion of various experts. It is not known whether CBD can detect the critically ill
in the UK system nor is it known whether it is safe to be used as a syste m of prioritising
by time of response. This work aims to determine whether the use of CBD is appropriate
for determining the timing of emergency ambulance response in the UK.
22
4.3. Review of Expert Opinion Study as an example of a cause for concern.
4.3.1 Introduction
The development of the CBD system which has been used in the UK since 1st April
1997 has been described earlier. The processes of consultation and expert committee
were not those described as good practice for consensus development 43.
The purpose of this study aimed to determine whether the development process of CBD
in the UK resulted in a system that had the agreement of experts. As with many areas,
there is controversy over who should be considered an expert, are they the consultants in
accident and emergency medicine, dispatchers or the paramedics? The ambulance
personnel with greatest clinical knowledge, the paramedics, do not have the same depth
of clinical knowledge as the medically trained staff, they rarely practice triage scoring
and do not have a detailed knowledge of dispatch systems. They are used to treating only
one or two patients to whom they have been dispatched. They therefore do not have to
make decisions regarding triage of patients on a regular basis and when this triage is
undertaken it is with sight of the patient. The dispatchers in the control room have expert
knowledge of the dispatching system, but do not have the medical expertise to determine
clinical urgency. Neither paramedics nor dispatchers have any formal sys tem of follow
up to enable evaluation of the prioritisation system. Their assessment is likely to be
based on anecdote and informal feedback from the subsequent information passed from
the attending crew to other personnel via the control room.
Consultants in accident and emergency medicine have expert knowledge of the clinical
conditions and they are familiar with the principles of triage as this is universally
employed in accident and emergency departments in the UK. However, they may not be
familiar with the particular difficulties relating to prehospital care and ambulance
dispatch. Only a small number of A&E consultants are actively involved in prehospital
care. Some of these are involved in training ambulance staff and immediate care doctors;
others are involved in strategic planning. Some are operational in prehospital care
attending incidents to administer clinical care. It was therefore decided that the most
appropriate panel of “experts” were consultants who are operationally active in
23
prehospital care. They would have an understanding of triage and the depth of clinical
knowledge of emergency medicine as well as an understanding of the difficulties of
prehospital care. Some may not be aware of the mechanisms of prioritised dispatch, but
this was considered a secondary problem. To compensate for this potential knowledge
gap, a panel of ambulance dispatchers was also used in the study.
4.3.2 Methods
Three methods were employed to assess expert opinion, drawing on three separate
panels (α, β & δ ). In all three studies, initial contact was made with potential experts.
The aim of the study was explained as well as providing an estimate of the time
involved, and provided they were asked whether they would be prepared to participate.
Those that agreed were provided with the appropriate information and proformata. For
the purposes of this study category “C” was defined as “those that are not emergencies
and can have a delayed response (as yet not defined by time)” and as being not identical
in time response to category B. This was to allow assessment of whether category “C”
can be used for an alternative response.
PANEL α and β
Experts: Consultants in accident and emergency medicine who are operationally active
in prehospital care, who are members of British Association for Immediate Care
(BASICS) or members of an active immediate care scheme.
Selection criteria: Identified from BASICS membership lists and the Emergency
Services directory. Those who agreed to participate were then randomly assigned
between panels α and β.
Method for panel α : A copy of the CBD coding system was sent to each expert with
instructions briefly outlined the dispatching system (Appendix three is an example of the
recruitment letter and appendix four is the instructions for panel α). The experts were
aware of the present code and were asked to state whether they believed this was correct,
over-triage or under-triage. Non-responders were contacted on two occasions by post or
e-mail.
24
Method for panel β: The experts were blind to the CBD codes and were asked to assign
a prioritisation code (A, B or C) to each presentation. The categories were maintained in
their chief complaint groupings of CBD but the order of the groupings and the
presentations within the chief complaint was defined by computer generated random
number selection. An example of a randomised sheet is included in table 4.3.1 compared
to the CBD sheet in table 4.3.2. The order of the chief complaints was also randomised.
Two reminders were sent to non-responders by mail or e-mail.
Table 4.3.1. Example of randomised CBD list as provided for panel β
Chief complaint
category
Symptom Prioritisation
code
Animal Bites Minor bite below neck non-poisonous
Unconscious or not breathing
Uncontrolled bleeding
Bite below neck with controlled bleeding
Bite from poisonous animal
Severe bites to face and / or neck
Difficulty in breathing
Swelling at bite site
25
Table 4.3.2. Example of CBD list (in CBD code book order) as provided for panel δ .
Chief complaint
category
Symptom Prioritisation
code
Animal Bites Unconscious or not breathing
Difficulty in breathing
Uncontrolled bleeding
Severe bites to face and/or neck
Bite from poisonous animal
Bite below neck with controlled bleeding
Minor bite below neck non-poisonous
Swelling at bite site
PANEL δ
Experts: 10 Ambulance dispatchers with at least 6 months experience of working with
CBD, employed by WMAS.
Selection criteria: Issued to a random sample of dispatchers.
Method: Each dispatcher was provided with a listing of the CBD codes and an
explanatory letter (see Appendix 5). These were in the order of the CBD book, that is in
alphabetical by chief complaint and then in prioritisation order of presentations within
the chief complaint (see table 4.3.2.). The dispatcher experts were asked to state
whether they believed this was correct, over-triage or under -triage. Non-responders were
contacted on two occasions by personal contact.
4.3.2 Results
Response rates
The response rates of each panel are demonstrated in table 4.3.3. Participation rates from
26
A&E consultants (panels α and β) were significantly higher than from ambulance
dispatchers (p<0.05 using fisher's exact test) as were response rates (χ 22df =4.11,
p<0.05).
Table 4.3.3. Participation and response rates.
contacted agreed to participate (%)
responses % response1
Panel α. 18 15 (83.3) 13 86.7
Panel β 13 12 (92.3) 11 91.7
Panel δ 20 12 (60.0) 10 83.3
1calculated as a percentage of those agreeing to participate
In 53 of the 324 (16.4%) categories, none of the members of the expert panels disagreed
with the present prioritisation code. Two of these were category “C” out of a total of 67
category “C” in CBD (UK). The remaining 51 were category “A” out of a total of 104
“A” categories. None of the 163 category “B”s had unanimous support. Details are given
in table 4.3.4.
Table 4.3.4. Expert agreement by CBD category.
CBD code
total codes in system
total agreement
50% or more in any group disagreed
A 104 51 13
B 163 0 101
C 57 2 37
TOTAL 324 53 151
In 151 (46.6%) categories 50% or more of experts for that method disagreed with the
coding. Details of all changes suggested by panel is summarised in table 4.3.5. The
distribution of changes suggested by 50% or over of the experts in any panel are shown
27
in figure 4.3.1 and the changes agreed by 50% or more of experts in all three panels are
demonstrated in figure 4.3.1.
Table 4.3.5. All changes proposed by expert panel
13 experts in group α ; 11 experts in group β; 10 experts in group δ Column totals indicate number of experts suggesting change; + indicates expert wanted upgrading (for example, +7, -1 means seven experts suggested upgrading and one suggested downgrading). Abdominal / Back Pain α β δ CBD
code Difficulty in breathing 12 to 50 years with
fainting / dizziness -1 -3 -5 1A2
Lower abdominal pain, female 12 to 50 years with fainting / dizziness
+3 +10 +2 1B1
Vomiting red blood +5 +9 +2 1B2 Abdominal / back pain, more than 50
years with fainting / dizziness +7 +11 +2 1B5
Fainting / dizziness when sitting up +4 +7 -1
-1 1B6
Side / back pain -3 -4 -7 1B7 Unspecified pain +1 +6 +3 1C1 Abdominal / back pain less than 50 years
(Non Traumatic) +7 +5 1C2
Allergic Reaction Fainting -1 -3 -6 2A5 Itching and/or rash with no difficulty
breathing +2 +7 +1 2C1
Concern about reaction but no history +6 +5 2C2 Reaction present for some time with no
difficulty breathing +6 +7 2C3
Animal Bites Uncontrolled bleeding +11 +11 +5 3B1 Severe bites to face and/or neck +5 +8 +8 3B2 Bite from poisonous animal +2 +10 +5 3B3 Swelling at bite site +1 +8 +4 3C2
28
Table 4.3.5.(contd.) Bleeding (Non Trauma) α β δ CBD
code Multiple fainting episodes +3 +9 +3 4B1 Fainting or near fainting when sitting +3 +9 -3 4B2 Vomiting blood (red / dark red) +4 +8 +2 4B3 Lower abdominal pain female 12 to 50
years with associated heavy vaginal bleeding
+4 +10 +2 4B5
Sweating +2 +8 +2 -1
4B6
Black tarry stools -1 +2 -1
-5 4B7
Vaginal bleeding more than 20 weeks pregnant
+2 +6 -1
+1 4B8
Bleeding without 'A' criteria +6 -1
-1 4B9
Uncontrolled nose bleed +6 4B12 Rectal bleeding without 'A' criteria +1 +6 +7 4C1 Breathing Difficulty Recent childbirth / broken leg /
hospitalisation within last 2-3 months +2 +7 +1 5B2
Drooling / difficulty swallowing +7 +9 +4 5B3 Asthma unresponsive to medication +7 +8 +6 5B4 Less than 50 years without “A” criteria -2 +1
–5 -7 5B5
Tingling or numbness in extremities or around mouth
+1 +11 +5 5C1
Chest Pain Male more than 35 years +1 +7 +2 7B1 Female more than 40 years +1 +8 +2 7B2 15 to 35 years with shortness of breath
/ nausea / sweating +1 +9 7B3
With drug abuse +1 +6 +2 7B4 Male less than 35 years without “A” or
“B” criteria +1 +9 +6 7C1
Female less than 40 years without “A” or “B” criteria
+1 +9 +7 7C2
Rapid heart beat without “A” or “B” criteria
+2 +6 7C3
Chest injury less than 35 years without “A” or “B” criteria
+2 +7 +7 7C4
29
Table 4.3.5.(contd.) Diabetic α β δ CBD
code Decreased level of consciousness +3 +10 +3 9B1 Fainting +6 +2 9B2 Chest pain +4 +11 +8 9B3 Unusual behaviour / acting strange +4 +9
-1 9B4
Not feeling well +1 +8 +1 9C2 Weakness +1 +8 +4 9C3 Fits / Convulsions Diabetic +4 +11 +1
0 11B1
Secondary to drug overdose +5 +10 +5 11B2 Fit unknown history +1 +9 +2 11B3 Fit / convulsion less than 6 years +2 -
1 +8 +5 11B4
First time fit more than 6 years +1 +6 +1 11B6 Gynaecological / Miscarriage Vaginal bleeding with fainting -1 -5 12A2 Fainting or near fainting when sitting
up -1 -8 12A3
Bleeding more than 20 weeks pregnant +2 +7 –1
12B2
Pregnant less than 20 weeks or menstrual with any of the following: cramps pelvic pain spotting
+8 +8 +5
+4 +4 +4
12C1
Headache Decreased level of consciousness +8 +11 +4 13B1 Mental confusion +8 13B2 Worst headache ever +2 +8 -2 13B3 Sudden onset +3 +6 -2 13B4 Headache without “A” or “B” criteria +1 +6 13C1
30
Table 4.3.5.(contd.) Mental / Emotional α β δ CBD
code Unusual behaviour associated with
diabetes +1 +11 -1 14B1
Known alcohol intoxication -3 -4 -7 14B6 Threats to self or others +6
-1 -1 14B7
Police request standby +3 +6 14C1 Overdose / Poisoning Difficulty in swallowing +1 +7 +7 15B1 Decreased level of consciousness +4 +11 +5 15B2 Ingestion of household cleaners +1 +7 -1 15B4 Acute alcohol intoxication less than 17
years -2 +6 15B5
Drug overdose with chest pain +3 +8 +3 15B7 Chemicals ingested
splashed on skin +6
+2 –1
-2 -4
15B9
Drug use without “A” or “B” criteria +7 +2 15C1 Alcohol intoxication without drugs
more than 17 years +6 +2 15C2
Pregnancy / Childbirth Fainting or near fainting when sitting
up -2 -1 -7 16A3
Delivery +6 +10 +7 16B1 Labour pains / contractions:
less than 2 mins 1st pregnancy less than 5 mins 2nd pregnancy
+1 +1
+6 +6 -1
-2 +2 -2 +2
16B2
Bleeding more than 20 weeks pregnant +2 +7 -1
+1 16B3
Waters broken +6 -1
+1 -2
16B7
Labour pains: more than 2 mins 1st pregnancy more than 5 mins 2nd pregnancy
+1 +1
+8 +8
+5 +5
16C1
Pregnant less than 20 weeks with abdominal pain spotting
+8 +7
+3 +4
16C2
31
Table 4.3.5.(contd.) Sick / Unknown α β δ CBD
code Decreased level of consciousness +4 +11 +1 17B2 Chest discomfort more than 35 years +3 +10 +1 17B3 Generalised weakness -7 -8 17B6 Other problems without other criteria +1
-7 -5 17B9
High temperature +2 +6 +2 17C3 Patient assistance +6 +1 17C4 Stroke / CVA Decreased level of consciousness +4 +9 +4 18B1 Chest pains +4 +11 +3 18B2 Diabetic +1 +9 +1
–1 18B3
Severe headache +2 +8 18B4 Trouble speaking -1 +7 -1 18B7 Unconscious Combined drugs and alcohol overdose -1 -6 19A3 Alcohol intoxication less than 17 years -5 -7 -7 19A5 Multiple fainting episodes +2 +8 +1 19B1 Fainting associated with
headache, chest pain / discomfort / palpitation more than 35 years diabetic / GI bleed. vaginal bleed sitting or standing abdominal pain female 12 to 50 years
+4 +4 +3 +4 +3 +3
+9
+11 +6
+10 +10 +10
+5
+3 +4 +1
19B2
Conscious with minor injuries -1 +1 -1
-7 19B5
Obviously dead - decapitated burned beyond recognition cold & stiff unless child less than 1 year
+1 +1 +1 +1
+1 +1 +3 +8
+2 +1 +2 +9
19C1
32
Table 4.3.5.(contd.) Miscellaneous α β δ CBD
code Chemical incident – stand-by +1 -
2 +3 -5 20B4
Riot incident +1 -1
+7 +2 -3
20B5
Fire Service - standby -2 +3 -6 20B7 Police - standby +2 +8 +4 20C2 Hoax call children +8 +2 20C4 Caller cleared unable to call back +1 +8 +5 20C5 Major incident exercise +1 +6 20C6 Assault / Trauma Decreased level of consciousness +5 +11 +10 21B1 Uncontrolled bleeding +9 +11 +10 21B2 Extremity/
femur fracture
+3 -2 +2
-6 21B6
Minor injuries w ithout weapons +6 +2 21C1 Police request standby or check
patient +6 21C3
Burns Decreased level of consciousness +6 +11 +5 22B1 Burns to airway, nose, mouth +11 +11 +9 22B2 Electrocution / electrical burns +3 +8 +2 22B3 Burns / scalds more than 15% of body
surface +6 +9 +4 22B4
Battery explosion +2 +7 22B5 Chemical burns to eyes +4 +9 -1 22B6 Freezer burns +1 +6 +6 22C2 Drowning Unconscious or not breathing 23A1 Confirmed submerged more than 1
minute +6 +10 +10 23B1
33
Table 4.3.5.(contd.) Falls / Accidents α β δ CBD
code Unconscious or not breathing 24A1 Severe difficulty breathing -8 24A2 Decreased level of consciousness +7 +1
1 +5 24B1
Amputation above fingers or toes +4 +9 +5 24B2 Patient paralysed +4 +1
0 +2 24B3
Uncontrolled bleeding +10
+11
+6 24B4
Fall more then 10 feet +3 +7 +4 24B5 Fall associated with chest pain, dizziness,
headache or diabetes +2 +6 24B6
Was unconscious but now conscious +6 24B7 Multiple extremity fracture or
single femur fracture +3 +3
+11
+9
24B9
Third party caller not with patient +6 +2 24B10
Patient assist / assessment +6 24C2 Isolated extremity fracture +3 +1
1 +2 24C4
Neck or back pain +5 +10
+7 24C5
Neurological / Head Injury α β δ CBD code
Decreased level of consciousness +7 +11
+1 25B1
Fall more than 10 feet +3 +8 +3 25B2 Aggressive behaviour +1 +1
0 +2 25B3
Now awake - has been unconscious +7 -1
25B4
Confused as to what happened +6 -2 25B5 Bump or laceration from fall without loss
of consciousness +7 +2 25C1
34
Table 4.3.5.(contd.) Road Traffic Accident α β δ CBD
code Decreased level of consciousness +5 +11 +5 26B1 Confirmed or unknown injuries with
the following mechanism:-
Vehicle vs. immovable object +3 +9 +2 26B2 Vehicle vs. vehicle (head side on) +3 +9 -2 26B3 Vehicle vs. pedestrian +5 +10 +3 26B4 Vehicle vs. motorcycle / bicycle +5 +10 +2 26B5 Victims trapped / ejected +8 +11 +7 26B6 Multiple vehicle / casualty incident +4 +11 +4 26B7 Chest pain prior to accident +5 +10 +5 26B8 Roll over +4 +8 +2 26B1
0 Third party caller not with patient +7 +3 26B1
1 Minor injuries patient up / out /
walking +1 +8 26C1
Patient assessment required by police +1 +6 26C2 Child under 2 years Croup
Asthma Epiglottitis
-6 -1
-2 -6
27A4
Animal bite -4 -9 -3 27A13
Sick / unknown / other -2 -5 -5 27A18
Mental / emotional -4 -10 -4 27A20
Abdominal / back pain -2 -10 -6 27A23
35
Area of overlap of all three represents where all three panels had 50% or more of experts who agreed a change was appropriate (n=7) Area of overlap represent where at least two panels had 50% or more of experts who thought change was appropriate (n= 4+7+28=309) Non overlapping areas represents where only that panel had 50% or more of experts who thought change was appropriate.
Figure 4.3.1. Summary of changes by panel suggested by 50% or more of the experts in
any panel - letters represent panel of experts not CBD codes
7
1
4
91 28 20
0
panel α
panel δ
panel
β
36
Table 4.3.6. Cases where 50% or more of experts in all panels suggested change.
CBD code
Chief complaint
Symptom No experts suggesting change
Panel α n
=13
Panel β n
=11
Panel δ n
=10 3B1 Animal
Bite uncontrolled haemorrhage 11 11 5
21B2 Trauma uncontrolled haemorrhage 9 11 10
24B4 Fall uncontrolled haemorrhage 10 11 6
24B1 Fall decreased conscious level 7 11 5
5B4 Asthma unresponsive to treatment 7 8 6
22B2 Burns to airway, nose, mouth 11 11 9
26B6 RTA victims trapped / ejected 8 11 7
In panels α and β there was only one case where 50% or more of the experts suggested a
downgrade (Alcohol intoxication less than 17 years - downgrade from “A”) except in
children under two. Panel δ, the ambulance dispatchers, had 50% or more of these
experts suggesting downgrade in 16 cases. The distribution of agreements and
disagreements is shown in Figure 4.3.1.
Children under two years are uniformly categorised as “A”. The experts had 50% or
more disagreement with this in five categories (20%) (see table 4.3.7).
Table 4.3.7. Disagreements by 50% or more of experts on a panel for categories
involving children under five.
Child under 2 years Panel α
Panel β
Panel δ
Present code
Croup
Asthma
Epiglottitis
-6
-1
-2
-6
27A4
Animal bite -4 -9 -3 27A13
Sick / unknown / other -2 -5 -5 27A18
Mental / emotional -4 -10 -4 27A20
Abdominal / back pain -2 -10 -6 27A23 . Minus indicates a downgrade suggested
37
Panel β was the only panel who was blinded to the original codes. Only in one (0.3%)
adult code did 50% or more of the experts downgrade and in 126 (38.8%) 50% or more
of the experts upgraded (34 of which were category “C” patients).
If 50% or more of each panel of experts were taken the distribution of codes would have
been changed as demonstrated in table 4.3.8. Expert panel β recommended most changes
with the eventual number of codes in each category after suggested changes being 156
codes in category “A” and only 36 in category “C”. The other two expert panels
opinions resulted in fewer changes, but both increased the number of category “A”
groups.
Table 4.3.8. Changes induced if decision of each 50% or more of experts on a panel
were used.
Present UK
system
Panel α
opinion
Panel β
opinion
Panel δ
opinion
A 104 115 156 118
B 163 152 132 152
C 57 57 36 54
TOTAL 324 324 324 324
4.3.4 Discussion
This study highlights the great variation in opinion of experts regarding the correct
coding of identified clinical conditions. Expert opinion from retrospective review has
demonstrated a high rate of disagreement about urgency even when working to the same
criteria 27. Dispatchers were more likely to downgrade codes. The A&E consultants were
less likely to disagree with the coding than the dispatche rs except when blinded to the
actual codes (panel β);.as demonstrated in figure 4.3.1. All three panels of experts
38
caused an overall upgrading of priority codes, with expert panel β causing the most
pronounced effect. This panel was blinded to the original codes and therefore represents
the expert's pre-existing opinion rather than one influenced by a suggested code. This
study suggests that CBD currently under-prioritises many types of patient compared to
expert opinion.
The panels of experts may be more likely to over-prioritise because they have no
incentive to give a low prioritisation, as this is a resource issue whereas allocating high
priority codes gives a larger safety net for clinical variation. There is a lack of objective
evidence base upon which to inform opinion, as there is an absence of literature on the
effects of delay on outcome in medical emergencies. The risk of a presenting symptom
being due to a specific condition that may need an urgent response is not accurately
known in many cases.
Fifty per cent or more of the experts on the panels believed that some changes should
occur in the category for children under 2, who are currently all given a category “A”
response. It is acknowledged that young children are difficult to assess and can
decompensate very quickly, leading to a rapid deterioration in their condition44. With
relatively low numbers of children under two, and therefore minimal resource
implications, (42 in this outcome study of 1598 patients = 2.6% - see chapter 6), the
speed of change in a child’s condition and the difficulty in the assessment of small
children, the Joint Royal Colleges Ambulance Liaison Committee advised continuing
the policy of all children under 2 receiving an “A” response. This section on children
also illustrates the possible risks of using clinically inexperienced experts (who are
experts in the process of dispatch) - 6 of 10 experts on panel δ suggested a downgrading
of the category for epiglottitis. This is a condition that is rapidly life threatening and
needs the care of specialists in hospital as a matter of extreme urgency.
The strongest recommendation from this study is that from when 50% or more of
experts in all three panels agree that change is required. This occurred for the presenting
complaints of uncontrolled haemorrhage, decreased conscious level, asthma
unresponsive to treatment, burns to the airway and victims of RTAs who are trapped or
ejected. This suggests that these should have a higher category. Differing complaints
resulting in the uncontrolled haemorrhage or decreased level of consciousness received
39
varying levels of support for change, some where 50% or more of the expert panel did
not suggest change.
The variations in opinion and the high rate of suggested change of the blinded pa nel
suggest that many of the current codes may not have the approval of 50% or more of
experts. However the variation in opinion demonstrated by the range of experts used in
this study strongly suggests the need to use a more objective method of assessing the
safety and effectiveness of CBD, such as the clinical outcome studies described later.
The only published work on safety of ambulance service prioritisation systems in the
UK, outside of the work undertaken by the author and his colleagues at the University of
Birmingham, has relied on expert opinion31. This study suggests that expert opinion may
be an unreliable means of assessing the safety of CBD. There is a need to critically
appraise methods of guidelines development and ensure that adequate piloting of any
system is instituted with outcome assessment before being disseminated for general use.
The process for establishing evidence based guidelines has been well described45.
Unfortunately this has not been done in the case of CBD with no systematic review of
the literature and decisions being made by committees rather than by consensus opinion.
The variation in expert opinion highlights the need for more evidence to inform
decisions in developing prioritisation systems. The clinical outcome and critical illness
studies undertaken in this thesis aim to augment the expert opinion studies already
undertaken and inform future developments.
4.3.5 Conclusions
Expert opinion can give highly variable results according to how information is supplied
to them and their specific areas of expertise. The high response rate of the panel
members in the first two groups suggests that the consensus view should be
representative of wider opinion by similar specialists.
This study would seem to suggest that certain code s need change. In 7 cases, 50% or
more experts on all three panels suggested codes that should have been changed – these
codes should be considered for change on this basis. In a further 32 codes, two of the
40
three expert panels had 50% or more of experts suggesting change. These categories
should be reviewed in association with other evidence to determine the need for change.
The 53 categories with complete agreement should continue to be monitored but are
unlikely to require change at present.
The variability of expert opinion demonstrates the need for outcome studies and other
research approaches to determine the correct coding of conditions for ambulance
prioritisation.
41
5. A SYSTEMATIC REVIEW OF THE EVIDENCE ON THE USE OF PRIORITY DISPATCH OF EMERGENCY AMBULANCES.
5.1 Introduction
The study of expert opinion of the CBD coding system has highlighted that CBD does
not have full support. Only 53 of 324 codes (16.3%) had support of 50% or more of
experts in all three expert panels. It is therefore important to determine whether the
coding system is based on good evidence and whether the system has undergone formal
evaluation.
The volume of primary research that aims to evaluate prehospital based practice continues
to increase and in many areas there appear to be several relevant publications, sometimes
with contradictory results and conclusions. The practice of evidence-based medicine
requires the identification of the majority of relevant articles before decisions are made.
Systematic reviews of the literature locate, appraise and synthesise evidence from existing
research and their advantages have been well described 46,47. It has been reported that use
of electronic MEDLINE searches alone are unlikely to identify all the relevant literature 48,
49, 50. The most effective method of identifying appropriate research publications has still
not been established.
Emergency medical dispatch systems (EMD) comprise a set of key questions, pre-arrival
instructions and dispatch priorities for medical emergencies that am bulance dispatchers
provide over the telephone51. Since the early 1990s there have been calls for the
implementation of a protocol-based dispatch system in the United Kingdom52. EMD
systems fall into two broad groups; medical priority dispatch and criteria based dispatch.
Medical priority dispatch systems differ from criteria-based dispatch systems by using
algorithms rather than prompts53. EMD has been utilised by emergency ambulance
services in the UK since 1997 to prioritise the allocation of ambulance resources to 999
calls for which the response time is crucial to the patient’s survival54.
A systematic review of the literature was undertaken to assess the existing literature
evaluating the effect of the priority dispatch of emergency ambulances on both clinical
outcome and ambulance utilisation. The aim of this study was to assess the sensitivity and
42
specificity of a wide number of potential sources of literature in detecting literature on
ambulance dispatch and to describe the relevant literature findings.
5.2 Methods
The literature search was designed to find all publications containing original data,
relating to the prioritisation of emergency ambulance calls. No restrictions were placed
on the type of study, method of analysis or on the language of the paper.
Three electronic databases were used, all searches commencing with the earliest date
available for the respective databases: Medline (using the Ovid interface, from 1963),
CINAHL (from 1982) and BIDS (from 1981). Medline is widely used by medical
researchers and is recognised to cover most of the high quality medical journals. CINAHL
covers an extra area - the nursing and paramedical sciences- not covered by Medline.
BIDS includes other scientific non-medical journals. The combination of the three was
aimed to cover the expected journals that may contain work relating to ambulance
services. The start date for the search on these databases was the earliest available for
each. The words “ambulance”, “EMS, “prioritisation”, “dispatch” and “triage” were used
in combination to search these indices (Table 5.1). Wild cards were also used ($ signifies a
wild card in most search engines). For example searching on prior$ will detect all words
starting with the first five letters prior, and therefore includes words such as prioritisation,
prioritising. The bibliographies of all relevant publications were searched to identify
secondary citations.
Table 5.1 Search strategy for electronic databases
Medline 1963 - 1997
Strategy: EMS (head) + prior$ or dispatch Dispatch Dispatch + EMS (heading) [Ambulance (heading) OR EMS (heading)] + prior$ Ambulance.sh + triage.sh/prior$.th/dispatch$.tw
43
Table 5.1contd BIDS 1981-1997
Strategy: “Ambulance” and “Dispatch” ambulance + prior$ + response ambulance + prior$ ambulance + dispatch ambulance = triage emergencies + dispatch CINAHL 1982-1997
EMS (head) + prioritise or dispatch Dispatch = 124 references Dispatch + EMS (heading) [Ambulance (heading) OR EMS (heading)] + prior$ Ambulance.sh + triage.sh/prior$.th/dispatch$.tw $ signifies a wild card in the search.
A request for details of any articles that may not have been identified by searching these
three bibliographic databases was made to researchers identified as being active in the
field. These researchers comprised authors of relevant papers identified from the searches
of the electronic databases or members of the National Academy of Emergency Medical
Dispatch in America. Requests for relevant articles were posted in the two main UK
prehospital care journals (Prehospital Immediate Care and Ambulance UK) and on four
Internet mailing lists (see Appendix 6) that were relevant to prehospital and emergency
medical care.
The tables of contents of key journals known not to be indexed on electronic databases
were, if possible, searched electronically (Emergency Medical Services, Journal of the
Emergency Medical Services, Fire Rescue, Prehospital Immediate Care, Prehospital
Emergency Care) or if necessary, hand searched (Journal of the British Association of
Immediate Care, 911, Ambulance UK).
All publications obtained from these sources were examined independently by 2 reviewers
for relevance to the review.
44
All articles were classified to one of four groups:
1 Studies of prioritisation where original data were presented.
2 Manuscripts that related to prioritisation but contained no original data.
3 Manuscripts that did not relate to prioritisation of emergency ambulance calls but did
relate to prehospital care.
4 Manuscripts unrelated to prehospital medical care or ambulance dispatch.
In cases where the two reviewers disagreed, a third reviewer also assessed the article to
achieve consensus. Articles that did not report original data or were not relevant to the
purpose of the review (groups 2-4 above) were excluded from further analysis.
Three independent reviewers (one expert in prehospital care in the UK, one expert in
prehospital care non-UK and one academic of at least lecturer status with experience of
critical appraisal) then considered the relevant articles against standard appraisal criteria
adapted from a previous review (see Appendix seven) 55. The experts in prehospital care
were selected from the membership of the British Association for Immediate Care who
were of consultant status or equivalent. Experts in prehospital care from outside the UK
were identified as authors in prehospital journals of consultant level or equivalent. The
academics were senior staff in the author’s department. The reviewers were allocated
randomly to the papers using a random number sequence; measures were taken to ensure
that no reviewer was sent a paper on which they were an author or a paper originating
from his department. Non-responders were contacted on one occasion. If there was no
reply after this approach, a further reviewer was allocated.
The quality of each paper was assessed by seven questions (1-7 on proforma, Appendix
seven). Each question was allocated one point for an answer corresponding to a good
paper (Yes for all questions except q3, where the preferred answer was no). The total
score for each expert was calculated and then averaged over the three reviewers to give a
score out of 7 for each paper. This is referred to as the quality score (QS).
Generalisability of the results to the UK ambulance service was assessed by four
questions. Question 3 was designed to exclude studies that did not look at either patient
outcome or resource usage. A similar scoring system was used as in the quality
45
assessment. A positive answer scored one point, whereas a negative response, “don't
know” or “not applicable” response scored zero.
Precision (the proportion of articles retrieved by a particular search strategy that were
relevant to the review) has been defined as the number of relevant papers identified by a
single source divided by the total number of references identified by that source.
Sensitivity (the proportion of articles relevant to the review retrieved by a particular
search strategy) has been defined as the number of relevant references identified by a
single source divided by the total number of relevant references.
5.3 Results
The sources searched yielded 326 unique references potentially eligible for inclusion in
the review of which 64 (19.6%) related to the prioritisation of emergency ambulances
and 20 (6.1%) related to prioritisation and also contained original data (see table 5.2).
Table 5.2. Classification of all articles identified.
Group N %
1 Studies of prioritisation where original data were presented
20 6.1
2 Manuscripts that related to prioritisation but contained no
original data
44 13.4
3 Manuscripts that did not relate to prioritisation of emergency
ambulance calls but did relate to pre-hospital care
91 27.9
4 Manuscripts unrelated to pre-hospital medical care or
ambulance dispatch
171 52.5
TOTAL 326 100.0
Table 5.3 shows a breakdown of the number of references identified by source with the
number found to be relevant and containing original data (n =20) (see appendix eight for
details of articles).
46
Table 5.3. Summary of results of literature search by database.
Source
Identifi
ed
Unique
Referenc
es
Identifie
d
Eligibl
e
High
Quality
Papers
Sensitivi
ty
Precisio
n
n n n n % %
Electronic Databases 242 157 10 4 50 4
MEDLINE 201 157 10 4 50 5
BIDS Science Citation Index
55 0 5 3 25 9
CINAHL 28 0 5 4 25 18
Cochrane Trials register
0 0 0 0 - -
NHS-CRD (DARE) 0 0 0 0 - -
Official databases 0 0 0 0 - -
Web Searches 0 0 0 0 - -
Yahoo 0 0 0 0 - -
Excite 0 0 0 0 - -
Non-cited journals 2 0 2 0 10 N/K
Electronic searches 0 0 0 0 - -
Hand searches 2 0 2 0 10 N/K
Personal contacts 47 38 11 4 55 23
Bibliographies 51 42 4 2 20 8
Unique references 326 20 7 - 6
Only half of the relevant references were identified by any of the electronic databases,
with 55% identified by people working in the field and only two (10%) by hand
47
searching. BIDS and CINAHL did not find any references that had not already been
identified by the Medline Search56. No relevant references were identified from
generalised Int ernet searches, official document databases, the Cochrane Randomised
Controlled Trials Register or the UK NHS Centre for Research and Dissemination
database of abstracts of research effectiveness (DARE) (Table 5.3.).
Only 7 papers (35% of the 20) were of high quality (average quality score of 4 or more)
(see Table 5.4).
Table 5.4. Papers relating to priority dispatch of ambulances and containing original data.
Author and year of publication
Cases included Outcome measures
Country n Quality score
Author’s conclusions
Bailey 199757 all number ALS crews dispatched
USA 6232 2.7 EMD reduces ALS crew usage. No under-triage rate quoted
Clark 199258 cardiac arrest bystander observing breathing
USA 445 4.0 46% cardiac arrests have agonal respiration at time of call
Clark 199459 cardiac arrest performance bystander CPR
USA 358 2.3 5.2% of cases received inappropriate CPR advice; 1.2% received inappropriate cardiac massage
Cordi 199760 bystander suspects death
confirmed death USA 127 2.3 95% accuracy of bystander reporting
Culley 199137 cardiac arrest performance bystander CPR
USA 267 3.7 bystander CPR rate increased from 34% to 54%. 2.3 minutes to give advice
Culley 199461 febrile fits & stroke paramedic response rates
USA NS 3.0 CBD decreases paramedic responses time but no Under-triage rate reported
Curka 199374 all use of ALS skills USA 14100 4.7 0.5% under-triage rate; 40% of cases only used BLS skills
Eisenberg 198562
cardiac arrest performance bystander CPR
USA 414 6.0 bystander CPR increased from 45% to59%
Eisenberg 198540 cardiac arrest presence of cardiac arrest
USA 516 1.7 caller >50 yrs or emotional suggests a high risk of MI
Herlitz (2) 199563 chest pain MI at hospital Sweden 503 4.7 historical risk factors important when classifying cases, in particular the presence of dyspnoea, vertigo, cold sweat, syncope or severe pain were recognised as high risk factors
49
Table 5.4 (cont.). Papers relating to priority dispatch of ambulances and containing original data.
Author and year of
publication
Cases included Outcome measures
Country
n Quality score
Authors Conclusions
Herlitz 199564
chest pain MI at hospital Sweden 503 5.7 39 of 143 who EMDs thought low risk had an MI
Hu 199665 all in rural area need for ALS China 594 3.7 high proportion of ALS cases are dead on arrival.
Key 199766 all ALS intervention USA 12049 2.3 7 of 12049 missed ALS cases because of failure/refusal to answer questions
Lagaert 199767 cardiac arrest presence of cardiac arrest
Belgium 311 2.3 delay of 3 minutes from collapse to call; 15% of patients had warning symptoms
Lammers 199568
abdominal pain cost evaluation USA 788 4.0 indiscriminate ambulance dispatch cheaper than prioritisation if under-triaged cases cost <$3674
Meron 199669 cardiac arrest location of caller, communication problems
AUSTRIA
114 3.0 55% callers in contact with patient; 92% able to follow instructions
NAEMSP 199570
intermediate dispatch category
ALS interventions USA 343 0.7 1.3 % of cases under-triaged
Palumbo 199671 all coding by EMD and physician
USA 320 3.0 43% agreement in priority coding between EMD and physicians; no under-triage rate reported
Slovis 198572 all response times & EMT diagnosis
USA 212 3.3 dispatch decreases the response time for urgent cases, 7% of cases are under-triaged
Sramek 199473 chest pain & unconscious
diagnosis at hospital
NL 1386 6.0 83-90% of MIs predicted by dispatchers
There are few papers containing original data about the use of prioritisation for emergency
ambulance calls. The majority of this literature (14 of 20 papers) originates from America.
Eight papers (40%) relate to cardiac arrest and 3 (15%) to patients suffering chest pain. Only
5 (25%) study all patients calling the emergency ambulance service.
The concept that CBD improves clinical outcome is supported by two papers, which both had
a quality score of 4 or more 73,41. Sramek73 showed that bypassing the general practitioner and
using the emergency ambulance service may result in less delayed transportation of patients
with potentially time dependa nt illness but does produce a higher workload of non-urgent
cases. It also showed a 55% rate of over-triage by dispatchers. This was an observational
study of calls to the emergency ambulance services in one rural and one urban centre, with
follow up to hospital when transported and follow up to the general practitioner when not
transported as well as using patient follow up by postal questionnaire. Urgency was assessed
by expert opinion of hospital based specialists. The study has several weaknesses and
therefore evidence is not strong but indicative. Eisenberg41 showed that after the introduction
of a programme of CPR advice from ambulance dispatchers, survival from cardiac arrest
improved. This was related to an increase in bystander CPR. This was a prospective study
before and after the introduction of CPR advice from dispatchers involving 346 patients. All
patients receiving resuscitation were included and survival to discharge from hospital was
measured. It appears well constructed without significant cause for bias.
Two papers with a QS of 4 or more74 75 and one with a QS of 337 supported the hypothesis
that CBD improves ambulance utilisation. Curka74 demonstrated that dispatch systems
could increase the availability of advanced life support units and target their use at more
serious cases. Culley61 confirmed this increase in EMS efficiency by improved utilisation of
advanced life support units. This study was a before and after study, using data obtained
from paramedic report forms. It used febrile convulsion and cerebro-vascular disease as the
marker conditions and did not study any other conditions. It did not measure outcome but
focused on need for paramedic intervention. This study does therefore look at a small group
of patients and excludes some groups with greater needs for emergency care, such as
cardiac disease. In the before study some data was not available for when requests for
paramedics were from other crews. Results of this study should only be applied to the
specified diagnostic groups and may be biased towards increased efficiency of the system
51
because of missing data. Helitz75 showed that dispatchers’ suspicion of acute myocardial
infarction did not affect outcome but did allow better use of resources. This study of 503
patients assessed dispatcher's suspicion of the presence of acute myocardial infarction,
using a questionnaire. The study does not state when this questionnaire was completed.
Follow up was via hospital record and evaluation by a single nurse and use of standard
criteria for diagnosis of myocardial infarction. There is a lack of detail of how those
discharged were followed up. This study may have some bias due to this last factor but it is
likely that this effect is small.
Only three papers were identified that were generalisable to the UK ambulance service,
where prioritisation is used to determine the speed of response rather than the skill level.
These three studies provided conflicting evidence; one study74 (Curka- details above)
reported that only 0.5% of those triaged to Basic Life Support subsequently needed an
Advanced Life Support intervention (QS=4.7). The second75 (Herlitz- details above) reported
that 39 out of 143 patients (27%) with chest pain considered low risk by the dispatcher had a
myocardial infarction (QS=5.7). The third76 reported that if the caller is over 50 years or is
very emotional this increases the risk of the cardiac arrest (QS=1.6). This study used data
collected as part of another study, collecting data from emergency call recordings. The study
reveals an association between these factors but cannot be said to be able to explore causal
relationships.
5.4 Limitations
Since two of the electronic databases (BIDS and CINAHL) only record publications
occurring since the early 1980’s it is possible that some relevant publications have not been
identified. However, of all the papers retrieved relating to ambulance dispatch, only four
were published prior to 1982 and none of these contained original data. The decision not to
hand search journals for manuscripts prior to 1982 does not appear to have affected the
number of relevant papers retrieved.
5.5 Discussion and Conclusions
Only 20 papers containing original data and relating to the effectiveness of priority dispatch
of emergency ambulances were identified. The overall quality of these publications was poor
with only seven (35%) papers having a quality score greater than or equal to 4. Establishing
52
the effectiveness of priority dispatch requires evalua tions that have a control group and that
measure outcome at both hospital arrival and discharge.
The evidence for improved outcome relates to improved advice to the caller and possibly, the
use of the ambulance services rather than a general practitioner. Improved ambulance usage
and efficiency results in systems where a choice between level of response (ALS vs. BLS) is
made. Most of the papers identified were studies from outside the UK and were not
considered to be generalisable to the UK ambulance service, because of differences in how
ambulance services operate overseas. Lack of generalisability was related to the populations
studied, the location of study and the means of prioritisation assessed.
This study has provided further evidence to demonstrate that electronic databases only
identify approximately half of all relevant prehospital literature48,49. The importance of
surveying experts when compiling a syste matic review has recently been questioned77.
However, almost a quarter (n =47, 23.4%) of all the references considered for inclusion in
this review were identified by people working in the field and eleven of these (23%) were
found to be eligible. Two of the four high quality papers identified by people working in the
field were not identified by any other source.
The lack of sensitivity of the electronic databases may be due to problems with indexing,
particularly since priority dispatch systems, in common with many other aspects of
prehospital medicine, do not have a unique coding in the databases. In addition, many of
the specialist journals are not currently indexed by the mainstream electronic databases.
Hand searching these journals was not a productive means of identifying literature relevant
to priority dispatch systems. Whether these findings are generalisable to all aspects of
prehospital care has yet to be determined.
This study supports work undertaken within primary care 78 which also identified that
individuals known to be undertaking research in the area of interest are an essential source
for identifying literature. However, blanket mailings of professional organisations with
standard letters are unlikely to be effective77. It is probable that, for personal contact to be
effective, personalised letters relating to well focused review topics should be sent to persons
known to be research active/aware. When performing a systematic review in the area of
53
prehospital care, the sources of literature utilised should include the electronic databases
supplemented by contact with appropriate experts.
The lack of good quality research relating to the prioritisation of emergency ambulance calls
is highlighted in this study. It is now apparent that CBD neither has good support from
experts nor from the evidence base. There is no evidence of high quality research of the
safety and effectiveness of the CBD system. There is a need for primary research to supports
the benefits, safety and effectiveness of CBD
.
54
6 CLINICAL OUTCOME STUDY
6.1 Introduction
Earlier work in this thesis has determined the need for a clinical outcome study by
demonstrating the lack of expert support for the present coding system and the lack of
existing evidence to support the system.
The aim of providing an ambulance or a paramedic quickly is to prevent patient
deterioration and to optimise care. Very few prehospital interventions have been proven to
be of value79. Urgency of prehospital care can be assessed in many ways, such as potential
diagnosis, final diagnosis, use of interventions at scene or interventions on arrival in
hospital. The need for an urgent intervention either at scene or on arrival at hospital
suggests that an emergency condition exists. Interventions may, however, be undertaken
prophylactically rather than as a treatment or may be inappropriate. It then becomes more
difficult to assess their importance. Hence, this prospective study looks at outcomes,
clinical state, interventions and expert opinion to determine urgency of care.
6.2 Setting
Accident and emergency department, City Hospital NHS Trust (CHT), Birmingham; a large
inner city A&E department of a university teaching hospital.
6.3 Inclusions
All 999 emergency ambulance cases presenting to City Hospital NHS Trust accident and
emergency department during four one-week study periods were analysed. the time periods
were chosen to cover a wide period of year to reduce any seasonal effects. The study
periods were:
• 07.59 hrs. Monday 28th July to 08.00 hrs. Monday 4th August 1997
• 07.59 hrs. Monday 18th August to 08.00 hrs. Monday 25th August 1997
• 07.59 hrs. Monday 13th October to 08.00 hrs. Monday 20th October 1997
• 07.59 hrs. Monday 3rd November to 08.00 hrs. Monday 10th November 1997
55
6.4 Exclusions
• Those patients being directly conveyed to the Birmingham and Midland Eye Centre.
• Those patients conveyed directly to the Labour ward.
• Any cases taken by ambulance from City Hospital catchment area to another hospital.
6.5 Methods
A cohort of emergency ambulance cases that were conveyed to the study hospital were
identified from West Midlands Ambulance Service and were then followed up. Outcome
data were established from a review of the ambulance service clinical records, hospital
notes and retrospective assessment of the dispatch category. Assessment was undertaken in
three ways –
1. expert opinion
2. interventions used in emergency phase
3. outcome.
Expert opinion was obtained on the “correct” prioritisation coding of each case in the study
using varying levels of information availability for the expert. This multi-level opinion was
used to model the effects of the varying levels of information available at various stages in
the process to help differentiate between incorrect prioritisation because of lack of
information and because of the limitations in the system utilised. Individual case review
was undertaken of a sample of cases where the dispatcher was perceived to have under-
triaged the case with respect to the expert opin ion. Interventions undertaken by the
ambulance crew or immediately on arrival in the accident and emergency department were
collated. The use of the various interventions was used on the assumption that if urgent
treatment was undertaken then speed of ambulance response would also be important.
Outcome measures were also collected and analysed with respect to CBD prioritisation.
Cases were identified from the West Midlands Ambulance Service NHS Trust control room
database by searching for 999 calls with C ity Hospital recorded as the destination hospital.
Complete case identification was enhanced by also searching the computerised record
system of City Hospital accident and emergency department for all cases arriving by
56
ambulance and excluding non-999 calls by review of notes and comparison with the
ambulance service database.
For all identified cases, data were obtained for analysis from:
• Ambulance Emergency Control Centre computer records
• Ambulance patient report form completed by attending ambulance crew
• Accident and emergency department notes from City Hospital.
Full details of the data collected is given in Appendix 3.
Data collected from the Ambulance patient information record included:
• Prehospital airway status
• Prehospital “AVPU” assessment of conscious level
• Spinal immobilisation undertaken
• Prehospital fluid resuscitation administered
• Prehospital drugs administered
Data were retrieved from the hospital records including:
• Monitoring after arrival in A&E
• Airway status on arrival in A&E
• Respiratory status on arrival in A&E
• “AVPU” on arrival in A&E
The dispatcher’s CBD category for each case was obtained from the West Midlands
Ambulance Service computer system. This is the code assigned under working conditions
and utilised for the management of the case by the ambulance service. Also collected from
the ambulance control record:
• Original time of 999 call
• Attendance time
• Time at A&E after 999 call
All the above information was abstracted and included on a proforma, an example of which
is Appendix nine.
57
6.6 Expert opinion
Expert opinion was obtained from four groups • Nurse opinion was given by the triage nurse at the time of arrival at the hospital • Expert A gave opinion using the CBD system • Experts B and C gave opinion using their professional expertise 6.6.1 NURSE OPINION
On arrival at the accident and emergency department, following initial assessment, the
triage nurse was asked to respond to two questions relating to the case:-
HOW URGENTLY WAS AN AMBULANCE REQUIRED FOR
THIS PATIENT? (please circle) 1. Immediate 2. Under 8
Minutes 3. Within 14 minutes 4. Within One hour 5.
More than 1 hour
REASON 1. ?airway problem 2. ?spinal injury 3. Short of
breath 4. Bleeding 5. ↓consc level 6. Fit 7. ?cardiac 8 Degree
of pain 9. Chronic problem, no recent change 10. Urgent treatment
required 88. Other (specify)
Figure 6.1 Triage Nurse ambulance prioritisation assessment form
6.6.2 EXPERT OPINION Having collected the above data, expert opinion was obtained on various aspects of the
prioritisation.
Expert A was the author of this thesis. At the time of data collection, he was an academic in
emergency medicine with special interest in prehospital care and experience in
prioritisation systems He has received training in ambulance dispatch and had recognised
higher qualifications in accident and emergency medicine and prehospital care.
58
Expert B was an experienced higher specialist trainee in accident and emergency medicine
with experience of receiving emergency cases from the ambulance service as well as being
responsible for the early management of such cases. He received a recognised higher
qualification in accident and emergency medicine soon after completion of this study.
Expert C was a general practitioner who undertakes prehospital care and works closely with
the ambulance service. He had a recognised higher qualification in prehospital care.
6.6.2.1. Expert A - “On Scene” CBD Code
Using only the information available from the control room and the ambulance report form,
a prioritisation category was assigned adhering strictly to the guidelines of CBD. The
expert used the CBD folder strictly according to the guidelines, in effect using them as
protocol rather than guideline. The full CBD code was used for this section. The expert
undertaking this coding was fully conversant with the performance of CBD and familiar
with the working of the emergency control centre and provision of prehospital care.
6.6.2.2. Expert A - “A&E” CBD Code
Using the information from all sources, (including information from hospital notes as well
as that available for the “On Scene” CBD code), expert A undertook a second coding
adhering rigidly to the CBD guidelines. Again the full CBD code was recorded. This
coding was done by the same person as the previous code but was not undertaken
sequentially, to avoid bias of knowledge of the previous code.
6.6.2.3. Expert B - “Dispatcher’s Expected” Code
For this code expert B uses the same sources of information as expert A in his assessment
(all those available by the end of the accident and emergency department history taking). It
is the prioritisation that expert B would have given had he been the dispatcher and been
able to obtain the relevant information via the telephone. The categorisation was made
independently of the CBD guidelines and were categorised to the codes in table 6.1. CBD
Category “A” is represented by 1 & 2 combined and Category “C” by 4 & 5 combined.
59
Table 6.1 Categories used by experts to define urgency.
Expert category
Response time Equivalent CBD category
1 Immediate response time 2 Response time less than 8 minutes
A
3 Response time within 14 minutes B 4 Response time within 1 hour 5 Response time more than one hour
C
6.6.2.4. Expert B - “On diagnosis” code
This was the expert’s prioritisation based on final diagnosis, ignoring earlier potential
diagnoses that have been disproven at any stage. A patient with neck pain after injury
would therefore have a high priority for a “Dispatcher’s expected” code, but a low code for
this category if it proved to be only a neck sprain. The same five point numerical codes
were used as for the expert “dispatcher’s expected” code.
The justification for the above urgency coding was classified according to table 6. 2
Table 6.2 Codes for justification of urgency of care.
Code Triage reason
1 Possible / actual airway problem
2 Possible spinal injury
3 Short of breath
4 Bleeding
5 Loss of consciousness / unconscious / knocked out
6 Fit
7 Possible cardiac / ? myocardial infarction
8 Degree of pain
9 Chronic problem, no recent change
10 Urgent treatment required
88 Other
98 Did not wait / self-discharge
99 Unknown / not specified
60
These categories were used to inform the case review of under-triage cases. 6.6.2.5. Expert C codes “on diagnosis”
Expert C undertook coding using the same guidelines as expert B for the "on diagnosis"
code only.
6.6.3. IMPORTANCE OF DATA COLLECTED 6.6.3.1. Dispatcher’s code Any error in the dispatcher’s code may be due either to failings in the CBD system,
dispatcher error, the dispatcher’s interpretation of the system or communication difficulties.
The communication difficulties may include difficulty in obtaining the information given in
the 999 call, misinterpretation of the information or false information.
6.6.3.2 Opinions Nurse
The nurse’s opinion was considered important as they were the only assessor in the study
who saw the patient. Therefore, if the data collection schedule had failed to include some
important variables or if actually seeing the patient was important, then this assessment
would be expected to be at variance with the other expert opinions listed below.
Expert A “On Scene” CBD Code
This reflects the prioritisation that should be achieved with optimal use of CBD using the
prehospital information. It presumes that communication difficulties are similar over the
telephone and in the A&E department.
Expert A “A&E” CBD Code
This reflects the code that optimal use of CBD would achieve if all the correct questions
were asked and with knowledge of the results clinical examination, investigations and
diagnosis. This code should therefore reflect the best result achievable by CBD.
Expert B “Dispatcher’s Expected” Code
This is the prioritisation that the expert would have given had he been the dispatcher and
been able to obtain the relevant information via the telephone. This therefore reflects what a
61
perfect system could achieve if it were infinitely flexible in response to individual
circumstances and could achieve 100% specificity and sensitivity.
Expert B “On Diagnosis” Code
This can be considered the gold standard. It is a code with the full advantage of
retrospection. The information available for this opinion included that from qualified
medical personnel following examination and investigation. This extent of information will
never be available from a 999 caller. Final diagnosis is defined as the diagnosis at the end
of the A&E episode, as recorded in the notes.
Expert C “Dispatcher’s Expected” and “On diagnosis” Codes
Use of a second expert to repeat those of Expert B improves the generalisability and
reliability of the expert opinion.
6.7 Qualitative case review of under-triage cases
After analysis of the expert opinion study was undertaken, those cases where it appeared
there had been under-triage were reviewed. In this study, under -triage was defined as any
case where the dispatcher or expert A had recorded a triage category lower than the “on
diagnosis” code of either expert B or C.
The author, with full control room information, ambulance patient report form, accident and
emergency notes and the experts’ opinions, reviewed all these cases. Review was
undertaken to determine potential causes of the under-triage. This in depth review was
undertaken for all under-triage cases in the first week of data collection.
6.8 Interventions
Prehospital treatment is usually limited to that which is urgent and that which prevents
deterioration en-route to hospital. All patients with an emergency intervention would be
expected to need an “A” category. The following prehospital interventions were noted:
• Monitoring
• Spine immobilisation
• Fluid resuscitation
• Drugs
62
• Other intervention - Most urgent action.
Emergency treatment in the accident and emergency department would also be expected to
correlate with needing the ambulance to arrive and transport the patient quickly, (that is
those needing a category “A” response. Hence the following data were obtained from the
accident and emergency department notes:
• Monitoring
• Urgent drug treatment
• Other urgent intervention
• Most urgent action.
6.9 Physiological status
If a patient is critically ill with abnormal physiological recordings then again urgency of
care is required. The following physiological data were recorded:
• Prehospital care Airway clear
• Prehospital care Breathing present
• Prehospital care “AVPU”
• Accident and emergency department Airway clear
• Accident and emergency department Breathing present
• Accident and emergency department AVPU
6.10 Outcome
Admission to hospital does not necessarily reflect urgency of care. Admission may be
necessary for observation or for treatment or investigation in the next 24 hours. However,
one would expect most CBD Category “A” patients to be admitted. Patients admitted to
Intensive Care or other critical care areas would be expected to be CBD Category “A”.
Data were therefore collected on the following outcome measures:
• A&E outcome (follow up arrangements, admission etc.)
• Days in-patient
• Days ITU
• Death during that hospital admission.
63
6.11 Other aspects
Duration of complaint was recorded since it would be expected that if a condition has been
present for more than 24 hours without deterioration, urgent response would not be
required. The triage score on arrival in A&E reflects the perceived urgency of care on
presentation in the accident and emergency department. This should correlate with urgency
of prehospital care. The triage category and reason for the categorisation were recorded.
This study pre -dates the implementation of the national triage scale and the nationally
accepted Manchester triage guidelines at the study hospital28.
• Prehospital care Triage Urgency
• Prehospital care Triage Reason
• Prehospital care 'Other' reason
• Most senior Doctor.
6.12 Reproducibility of expert opinion
In order to verify the consistency of the expert's opinions, a random sample of 20 cases
from each week were coded by each expert on two separate occasions. The experts were
blind to this procedure with no access to their previous codings.
6.13 Results
During the four data collection weeks, 1844 cases were identified on the City Hospital
accident and emergency department database that were labelled as having arrived by
ambulance. These were then validated initially with hospital records and then on the
WMAS database. 268 cases were excluded because they were not 999 emergency calls
(118 GP referrals, 11 St John Ambulance, 25 clerical errors or duplicate entries, 105 999
call made outside the study period, 9 transfers or other ambulance services). Analysis of the
WMAS database revealed a further 23 cases that were not on the CHT database. No cases
were identified and confirmed as 999 calls on the CHT database that were not on the
ambulance service database. (See Table 6.3)
64
Table 6.3. Sources of data for outcome study.
Detected on CHT database Total
Yes No
Yes 1576 23 1599 Detected on
WMAS database No 0 0 0
Total 1576 23 1599
There were 1599 cases available for this analysis from the four data collection weeks. One
of these cases did not have any CBD code assigned by a dispatcher in the emergency
control room.
In one case there was incomplete dispatcher information; in 21 cases incomplete A&E
information; 47 for chief complaint and condition and 46 for priority cases of incomplete
information for “on scene” coding. For the “expert expected” codes 52 were incomplete
but became 58 when coded the same as CBD due to 3 cases where the expert had
insufficient information and used an “insufficient information” code. For the expert “on
diagnosis” there were 121 cases incomplete, which became 133 on conversion to CBD,
again due to insufficient preceding information for the expert to make a decision. For expert
C “on diagnosis” codes 19 were incomplete, and for expert C there were 20 incomplete
when converted to codes.
Of the 1598 cases for which dispatcher information was available, the CBD coding
allocated by the ambulance service dispatcher is shown in table 6.4.
Table 6.4 Distribution of study patients by CBD category.
CBD category No. %
A 463 29.0%
B 918 57.4%
C 217 13.5%
65
There were 688 (43.0%) females and 910 (57.0%) males in the study. No significant
difference was demonstrated in the CBD classification by sex (χ2 = 2.37; p = NS; see table
6.5).
Table 6.5. CBD coding by sex of patient.
CBD
category
Category
“A”
Category
“B”
Category
“C”
no code
available
TOTAL
Male 257 537 116 0 910
Female 206 381 101 1 688
TOTAL 463 918 217 1 1599
% 28.9% 57.4% 13.6% 0.6% 100.0%
ϖ2 = 2.37. p = NS
The age distribution of the patients in this study is demonstrated in table 6.6. Categories
were determined by the data collection system already in place. Variation of CBD code
distribution by age category is also shown in table 6.6, this demonstrates a lower percentage
of category A in the young adult groups.
Table 6.6. Variation of category distribution by age groups.
Age Category “A”
% in age
group coded “A"
Category “B”
Category “C”
Total % of total in specified
age group
Under 2 39 92.9% 2 1 42 2.60%
2-11 23 28.8% 40 17 80 5.00%
12-17 17 18.7% 61 13 91 5.70%
18-34 97 20.6% 313 59 470 29.40%
35-64 139 28.4% 295 55 489 30.60%
65+ 148 34.7% 207 72 427 26.70%
Total 463 29.0% 918 217 1599 100.0%
66
0.0%
10.0%
20.0%
30.0%
40.0%
50.0%
0 2 4 6 8 10 12 14 16 18 20 22 24
hour of day
The mean hourly volume of the 999 calls varies during the day. From early morning the
level rises to a peak in the late morning, then fluctuates during the working day and falls in
the early evening. It rises again in the late evening before falling overnight. Details are given
in figure 6.2. The proportion classified as CBD “A” varies from 15% -45% during the day as
demonstrated in figure 6.3.
0
20
40
60
80
100
120
00 02 04 06 08 10 12 14 16 18 20 22
Time of day
No casesCBA
Figure 6.2. Time of 999 call vs. CBD category.
Per
cent
age
of c
alls
Figure 6.3.
Percentage of calls classified as category “A” per hour.
67
885 (55.3%) of the 1599 incidents occurred in the home.
A wide range of diagnoses were observed in the study. The diagnoses from the accident and
emergency notes are summarised in table 6.7. Soft tissue injuries and ailments and non-life-
threatening head injuries account for nearly a quarter of all 999 calls transported to AEDs
(23.5%). Severe trauma accounted for 0.5% of all cases with a further 3.8% of cases having
long bone fractures, 31.9% of cases were trauma related. Cardiac conditions accounted for
7.0% of cases with 0.9% of all cases presenting with a cardiac arrest and 4.1% with either
myocardial infarction or unstable angina. Respiratory disorders account for 5.8% of cases
with asthma being responsible for 1.6%. Other presentations relate to drugs and alcohol
(7.8%); abdominal pain (7.0%); fits (5.0%); collapse of unknown cause (4.4%); psychiatric
problems (3.1%); acute neurological problems (2.3%); non-trauma musculo-skeletal
problems (1.5%) and early pregnancy problems (1.2%).
Table 6.7. A&E diagnosis of cases in the study.
Chief complaint No. % of all cases % with diagnosis
Abdominal pain acute 40 2.5 2.7
Abdominal pain minor 72 4.5 4.8
Allergy 3 0.2 0.2
Arthropathy 1 0.1 0.1
Asthma 26 1.6 1.7
Back pain neuro loss non trauma 2 0.1 0.1
Back pain no neuro loss non trauma
21 1.3 1.4
Cardiac acute other 35 2.2 2.3
Cardiac arrest 14 0.9 0.9
Cardiac chronic 8 0.5 0.5
Cardiac MI/unstable angina 70 4.4 4.7
Collapse/faint 71 4.4 4.7
Cut/laceration - bleeding 44 2.8 2.9
Cut/laceration - not bleeding 20 1.3 1.3
Dehydration - all causes 8 0.5 0.5
Drug/alcohol overdose - minor 56 3.5 3.7
Drug/alcohol overdose - significant 68 4.3 4.5
68
Table 6.7 (contd.) Chief complaint No. % of all cases % with diagnosis
Facial fracture - no significant head injury
7 0.4 0.5
Facial injury - no fracture/head injury
41 2.6 2.7
Fit – febrile 25 1.6 1.7
Fit – non-febrile 55 3.4 3.7
Foreign body – non-urgent 3 0.2 0.2
Foreign body - urgent/complicated 1 0.1 0.1
Fracture/dislocation - hand/foot 28 1.8 1.9
Fracture/sprain/dislocation - major limb
60 3.8 4.0
GI bleeding 15 0.9 1.0
Head injury – moderate – minor - no x-ray
76 4.8 5.1
Head injury – moderate - needs
X-Ray/admission
74 4.6 4.9
Head injury - severe GCS<8 2 0.1 0.1
Infection - life threatening 1 0.1 0.1
Infection - minor 47 2.9 3.1
Infection - serious 27 1.7 1.8
Joint degenerative 1 0.1 0.1
Multiple - severe/moderate injuries 4 0.3 0.3
Neurological loss/stroke 37 2.3 2.5
Pregnancy related problems 18 1.1 1.2
Psychiatric/behavioural 50 3.1 3.3
Respiratory - minor 22 1.4 1.5
Respiratory - moderate 31 1.9 2.1
Respiratory - severe inc. choking 15 0.9 1.0
Soft tissue disorder - non trauma 77 4.8 5.1
Soft tissue injury 148 9.3 9.9
Trauma - life threatening 2 0.1 0.1
Other 74 4.6 4.9
Unknown 99 6.2
TOTAL 1599 100.0
69
6.13.1 Expert opinion In this section expert opinion determines under or over triage. Under-triage is where an
individual records a lower category than the expert. This means the patient receives a lower
priority ambulance response than is thought to be required. Over-triage is where an
individual records a category higher than the relevant expert. This means that the patient is
receiving a level of response higher than is thought to be required by the expert.
Internal consistency of results by experts The consistency of coding by the experts was assessed by them undertaking duplicate
coding for 20 cases each week. The experts were blinded, so they were unaware of their
previous coding or of which cards were duplicates. Kappa scores were calculated to
quantify the consistency of each expert. Expert A has good consistency in both the “on
scene” CBD code (coding by the CBD system using the prehospital information) with a
kappa score of 0.671 and in the “A&E”-CBD code (coding by the CBD system using both
accident and emergency department and prehospital information) kappa score 0.676. Expert
B had moderate consistency in his codes whether by information from the notes (kappa
score 0.524) or on final diagnosis (kappa score 0.481). Expert C had good consistency for
his coding based on final diagnosis (kappa 0.730). See table 6.8.
Table 6.8. Internal consistency of experts.
Expert Code Kappa Consistency
Expert A On scene CBD 0.671 good
Expert A AE-CBD 0.676 good
Expert B Notes information 0.524 moderate
Expert B on diagnosis 0.481 moderate
Expert C on diagnosis 0.730 good
70
Expert Opinion The analysis of expert opinions is summarised in table 6.9. This demonstrates that
compared to the CBD system (as undertaken by expert A; table 6.9 rows 1&2) the
dispatcher under-triages by 8-9% and over-triages by 31 %. When compared to expert B
who was looking at the information independently the dispatcher under-triages by 33% and
over-triages by 22% (table 6.9 row 3); this changes to under-triage of 17-38% and over-
triage of 40-54% when compared to the experts opinion based on final diagnosis (table 6.9
rows 4&5).
When looking at the CBD system (as judged by expert A results), it under-triages by 45%
and over-triages by 12% compared to expert B using the same information (table 6.9 row
6). When compared to the gold standard of final diagnosis the under-triage rate is 13-25%
and the over-triage rate is 27-39% (table 6.9 rows 7&8). If expert A only used the
information from ambulance recor ds (on scene), the under-triage rate is unchanged at 45%
and the over-triage rate minimally changed to 13% (table 6.9 row 9). The rates against final
diagnosis are also very similar with under-triage of 13-26% and over-triage of 27-39%
(table 6.9 rows 10 & 11).
The benefit of the final diagnosis is demonstrated by comparing expert B diagnosis using
accident and emergency department notes with final diagnosis which shows a 1% under-
triage but 53% over-triage (table 6.9 row 13). Looking at expert C in the sa me way gives
results of 12% under-triage and 38% over-triage (table 6.9 row 14).
When the A&E triage nurse’s categorisation was compared with that of expert B (notes
only) it showed 25% under-triage and 21% over-triage (table 6.9 row 16).
Dispatchers under-triaged 16.7% (n =245) cases when compared to opinion of expert B on
final diagnosis and 38.2% (n=604) cases when compared to expert C.
71
Table 6.9. Analysis of Coding by Dispatchers and Experts.
Row ref. no.
% Under-triage
% Over-triage
Kappa score
internal consistency
1 Dispatcher vs. A&E CBD system 9 31 0.346 fair 2 Dispatcher vs. On scene CBD system 8 31 0.351 fair 3 Dispatcher vs. Expert B “notes info” 33 22 0.164 poor 4 Dispatcher vs. Expert B “on
diagnosis” 17 54 0.079 poor
5 Dispatcher vs. Expert C “on diagnosis"
38 40 0.140 poor
6 A&E CBD system vs. Expert B “notes info” 45 12 0.181 poor 7 A&E CBD system vs. Expert B “on
diagnosis” 13 39 0.203 poor
8 A&E CBD system vs. Expert C “on diagnosis"
25 27 0.251 fair
9 on scene CBD
system vs. expert B notes info 45 13 0.163 poor
10 on scene CBD system
vs. expert B on diagnosis 13 39 0.195 poor
11 on scene CBD system
vs. Expert C “on diagnosis"
26 27 0.244 fair
12 on scene CBD system
vs. A&E CBD system 2 2 0.931 very good
13 Expert B “notes
info” vs. Expert B “on
diagnosis” 1 53 0.255 fair
14 Expert B “notes info”
vs. Expert C “on diagnosis"
12 38 0.243 fair
15 Expert C “on
diagnosis" vs. Expert B “on
diagnosis” 9 36 0.311 fair
16* Nurses vs. Expert B “notes info” 25 21 N/A N/A 17* Nurses vs. Expert B “on
diagnosis” 9 21 N/A N/A
*week one data only
72
Of the 245 cases under-triaged by the dispatcher, in expert B’s opinion, 93 cases were also
undercoded by the CBD system (expert A). The latter undercoded a further 185 that were
not undercoded by the dispatcher when compared with expert B diagnosis.
Of the 604 cases under-triaged by the dispatcher, in expert C’s opinion, 268 were also
undercoded by the A&E CBD coder. The latter undercoded a further 398 cases when
compared with expert C diagnosis.
Dispatcher error rate can be defined as the proportion of the total cases that that were
under-triaged solely by the dispatcher. The system error rate is the proportion of total cases
that are under-tria ged by the system and by the dispatcher using the system. The expert
discrepancy rate is the proportion of the total cases that only the expert A under -triaged -
this represents a summation of expert error plus those cases where the dispatcher improved
on the system. The gold standard is the expert's opinion when they had all information
available (the opinion as close to actual clinical requirement as can be achieved). These
rates can be calculated relative to each of experts B and C and are therefore quoted as a
range. (table 6.10)
Table 6.10 Error rates of CBD
using Expert B using Expert C Rate
Dispatcher error 152/1466 336/1578 10.3% - 21.3%
System error rate 245/1465 604/1572 16.7% - 38.4%
Expert discrepancy rate 185/1465 398/1572 12.6% - 25.3%
6.13.2 REVIEW OF UNDER-TRIAGE CASES
In week one, there were 37 under-triage cases, identified by either expert B from their “on
diagnosis” code or C. In only three cases (8.10%) could the under-triage be attributed solely
to the dispatchers. This represents a dispatcher error rate of 0.98% (3 of 304 cases). In 12
cases expert A under-triaged cases that were not under-triaged by the dispatcher,
representing an additional 3.9% error rate.
73
Under-triage only by dispatchers - case summary Case 1. A case of severe left ventricular failure that presented as a hypoxic fit
(no specific CBD code available) was miscoded as a fit of unknown origin (11B3).
Case 2 A person choking where it was probably difficult to differentiate
between mild difficulty in breathing and talking normally. This made no clinical difference
as the call was during the recovery phase after back slaps and successful expulsion of the
obstructing food.
Case 3 A diabetic who was alert but unwell and was therefore classified as
9C2. By the time the ambulance crew arrived 5 minutes later, he was pale and clammy
(therefore then 9B5) because of hypoglycaemia. Although theoretically correct at the time
of prioritisation, CBD should have a predictive element to allow for deterioration of the
patient before the ambulance arrives.
Under-triage by both dispatcher and expert A - case summary by diagnostic group
Diabetic patients only accounted for 6 patients in the study but 3 were under-triaged.
In one case it was A&E expert error in failing to note the patient was diabetic.
One has been described above. The third was a patient with peritonitis who was labelled as
diabetic with decreased conscious level (9B1).
Two cases were associated with use of the “fit unknown history” (11B3) category, which
was used on only eight occasions. Two further cases were mistriaged by the expert because
the fits were continuing at the time of the 999 call but had stopped by the time the crew
arrived and were therefore coded by the dispatcher as “fitting more than 5 minutes” (11A2)
or “unconscious” (11A1).
12.6% of trauma cases were under-triaged. Half of these were classified as “C” when the
experts B & C “on diagnosis” believed they should have had a Category “B”. Three road
accidents were classified according to mechanism of injury when clinical needs suggested
that they were more urgent. Three people had head injuries classified as 25C1 (bump or
laceration from fall with no loss of consciousness), although in two head injuries, the
dispatcher classed these as 21B7 (assault) and therefore gave it the correct category. One
74
fall of over ten feet (24B5) was graded an "A" by the expert. The final case was a burns
victim with an electric shock (22B3).
6.13.3 INTERVENTIONS
Only one third of those patients (n =390, 34.5%) being monitored before arrival in A&E were
categorised as “A”, but 58.5% (n = 152) of those monitored in the accident and emergency
department were so classified. Only 2 of the 35 (5.7%) patients needing spinal immobilisation
were categorised as “A”, but 67 (78.8%) of those needing drugs and 8 (40%) of those needing
fluids received the most urgent category. Of those who received urgent drug treatment on
arrival in A&E, 18 (50.0%) had received a category “A” response. 13 (65%) cases having
other urgent interventions in the accident and emergency department were similarly
categorised. In the case of fluid resuscitation, drug usage, other interventions and monitoring
in A&E, these were not significantly associated with allocation to category “A” (see Figure
6.11 for details). Significance of the differences between the intervention group and the whole
study population (control , line 1 of table 6.11) was tested using the Chi squared test. Testing
the hypothesis that patients are coded to “A” irrespective of any intervention required. In an
optimal system, all the patients above would have been categorised “A”.
Table 6.11. Interventions in relation to CBD status.
Category
A
Category
A %
Category
B
Category
C
TOTAL χ2
P = ***
Control 463 29.0 918 217 PHC Monitoring 390 34.5 608 131 1129
(70.6%) 4.81 p<0.05
PHC Spine immobilisation
2 5.7 27 6 35 (2.2%)
9.41 p<0.05
PHC Fluid resuscitation
8 40.0 10 2 20 (1.3%)
1.196 p = NS
PHC Drugs 67 78.8 17 1 85 (5.3%)
108 p = NS
PHC other intervention
277 46.7 279 37 593 (37.1%)
144 P =NS
A&E monitoring 152 58.5 99 9 260
(16.3%) 131 P =NS
A&E Urgent drug treatment
18 50.0 16 2 36 (2.3%)
7.9 P<0.01
A&E other urgent intervention
13 65.0 7 20 (1.3%)
12.7 P<0.001
75
6.13.4Physiological status
Two thirds (n =11; 68.8%) of patients with obstructed airway or absent breathing noted by
the ambulance crew in the prehospital phase were categorised as “A” by the call taker.
However, less than half (n=46.7%) of those with obstructed airways on arrival in A&E had
been categorised “A”. Similar numbers of those with a decreased conscious level in
prehospital stage (n =35; 59.3%) and on arrival in the accident and emergency department
(n =29; 65.9%) had been coded as “A”. Of those who were unconscious, but had a clear
airway and were breathing, a lower percentage were categorised as “A” 23 (54.8%) by the
prehospital assessment of unconsciousness and 16 (59.3%) by accident and emergency
department assessment. In the case of prehospital and accident and emergency department
conscious level, these were not significantly associated with allocation to category “A”.
Details are in Table 6.12.
Table 6.12. Physiological status in relation to CBD code.
Category
A
% with
cat A
Category
B
Category
C
TOTAL χ 2=
p = ***
Control 463 29.0 918 217 PHC Airway NOT clear 11 68.8 4 1 16 (1%) 12.4
p<0.001
PHC Breathing NOT present
11 64.7 5 1 17 (1%) 10.6
p <0.001
PHC AVPU = P or U 35 59.3 23 1 59
(3.7%)
27.4
p = NS
A-A&E Airway NOT clear
7 46.7 8 15
(0.9%)
2.3
p <0.05
B-A&E Breathing NOT present
14 63.6 8 22
(1.4%)
13.02
p<0.001
D-A&E AVPU = P or U 29 65.9 15 44
(2.8%)
29.99
p = NS
In an optimal system, all the patients above would have been categorised “A”.
76
6.13.5 OUTCOME 240 (25.2%) of the patients discharged from A&E were allocated to category “A” by the
dispatcher and 125 (13.5%) by the CBD system used strictly by expert A. Only 153
(16.1%) were categorised “C” by the dispatcher; 323 (34.7%) by the CBD system. Full
details are in Table 6.13.
Table 6.13. Discharge from A&E in relation to CBD code.
Information used “A” “B” “C” total % “B” &
“C"
All cases 463
29.0%
918
57.4%
217
13.6%
1599
100%
86.4%
Dispatcher 999 call 240
(25.2%)
559
(58.7%)
153
(16.1%)
952 74.8%
CBD
system
prehospital 125
(13.5%)
482
(51.8%)
323
(34.7%)
930 86.6%
10% (n =37) of admissions were categorised “C” by the dispatcher and 16.9% (n =60) by
the CBD system. Full details are in table 6.14.
Table 6.14. Admission to hospital in relation to CBD code.
Information
used
“A” “B” “C” total % “B” &
“C”
All cases 463
29.0%
918
57.4%
217
13.6%
1599
100%
86.4%
Dispatcher 999 call 130
(35.2%)
202
(54.7%)
37
(10.0%)
369 64.8%
CBD system prehospital 93
(26.0%)
204
(57.1%)
60
(16.9%)
357 73.9%
77
Category “A” was only assigned to 36 (41%) of those admitted to coronary care or high
dependency units (32; 35.2% for CBD system; (see Table 6.15) and to 2 (28.5%) of the cases
admitted to the intensive care unit from A&E (see Table 6.16). No cases admitted to ITU
from A&E were categorised as “C”. A further 6 patients were subsequently admitted to ITU.
Analysis of all admissions reveals that 8 (61.5%) were categorised as “A” by dispatchers (n
=6; 46.2%). Of the 13 patients admitted to ITU, in 4 (30.8%) cases the dispatcher and all
three experts agreed on a CBD code “A”. In one further case (7.7%) only one expert
disagreed and the others agreed on a code “A”. In one case (7.7%) all agreed that he should be
coded “B” or “C” with a dispatcher code “B”. In 6 cases there appears to be an error in the
CBD system in that expert A (using the CBD system) classified them as category “B” but
experts B & C classified then as a category “A”. In three cases the dispatcher over -triaged
according to CBD giving them the correct category “A”.
Table 6.15. Admission to Coronary care or High dependency in relation to CBD code.
Information used “A” “B” “C” total % “B” &
“C”
All cases 463
29.0%
918
57.4%
217
13.6%
1599
100%
86.4%
Dispatcher 999 call 36
(41.3%)
50
(57.5%)
1
(1.1%)
87 58.6%
CBD system prehospital 32
(35.2%)
59 (65%) 0
(0%)
91 64.8%
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Table 6.16. Admission to Intensive Care unit in relation to CBD code.
Table 6.16a ITU admissions direct from A&E
Information
used
“A” “B” “C” total % b & c
All cases 463
29.0%
918
57.4%
217
13.6%
1599
100%
86.4%
Dispatcher 999 call 2
(28.5%)
5
(71.4%)
0
(0%)
7 71.4%
Table 6.16b all ITU admissions, including admissions subsequent to A&E
Information
used
“A” “B” “C” total % b & c
All cases 217
13.6%
1599
100%
86.4% 1599
100%
86.4%
Dispatcher 999 call 8
(61.5%)
5
(38.5%)
0
(0%)
13 38.5%
CBD system prehospital 6
(46.2%)
6
(46.2%)
1
(7.6%)
13 53.8%
Three quarters (12; 75%) of patients dying in A&E or before arrival, were categorised as
“A”, although this rose to 93.8% using the system strictly applied by expert A. The
dispatchers did not categorise any of these early deaths as category “C”. Details are in table
6.17. Thirty-two patients in the study died after leaving A&E. Subsequent deaths during
hospital stay were, however, classified as category “C” in 3 (9.3%) cases by dispatchers and
3 cases (9.6%) by the CBD system. Half of the patients who subsequently died were
classified as “A” (n =17; 53.15 by dispatchers; n =14; 45.1% by CBD system). Of those
who died, the average duration of complaint was 12.5 hours (range 0.1-200 hrs.,
interquartile range 0.18-7). They were in-patients for an average of 14.28 days prior to
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death (range 1-57 days; interquartile range 3-22 days) and spent 0.88 days on ITU (range 0-
21 days; interquartile range 0 days).
Table 6.17. Deaths in relation to CBD code.
6.17 a Deaths before arrival at or in A&E
Information
used
“A” “B” “C” total % b & c
All cases 463
29.0%
918
57.4%
217
13.6%
1599
100%
86.4%
Dispatcher 999 call 12
(75%)
4
(25%)
0
(0%)
16 25.0%
CBD system prehospital 15
(93.8%)
0
(0%)
1
(6.3%)
16 6.3%
6.17 b deaths after leaving A&E during hospital stay
Information
used
“A” “B” “C” total % b & c
All cases 463
29.0%
918
57.4%
217
13.6%
1599
100%
86.4%
Dispatcher 999 call 17
(53.1%)
12
(37.5%)
3
(9.3%)
32 46.9%
CBD system prehospital 14
(45.1%)
14
(45.1%)
3
(9.6%)
31 54.8%
6.13.6 OTHER ASPECTS 1462 patients (91.48%) had data on the duration of their complaint. The duration of
complaint is summarised in Table 6.18. 136 (9.3%) had a duration of complaint of over 12
hours. Of these 9 (6.6%) were categorised as “A”, 39 (28.7%) as “B” and 88 (64.7%) as
“C”.
80
Table 6.18. Duration of complaint in relation to CBD code.
Cat A Cat B Cat C TOTAL ITU admissions
< 1 hr 117 276 493 886 8
1-2 45 80 105 230 1
3-6 17 47 50 114 2
7-12 17 47 32 96 0
13-24 8 18 34 60 1
25-48 1 13 23 37 0
49-72 0 5 18 23 0
72+ 0 3 13 16 1
Total 205 489 768 1462 13
6.13.7 RESPONSE TIME RESULTS The standards for response times for urban ambulance services using CBD is:
• Category “A” 75% cases within 8 minutes
• Category “B” 95% cases within 14 minutes
• Category “C” 95% cases within 14 minutes
The response times in this study for each CBD category did not show any statistically
significant variation by CBD category (χ2=6.6 (4df), p = NS ) (see table 6.19 for details).
The new response standard ( effective from 2001) of 8 minutes for category “A” calls was
achieved in 73.6% of cases and the 14 minute standard was achieved in 98.0% of category
“B” cases and 98.1% of category “C” cases.
Data on response times was available in 1578 (98.74%) of patients in the study. The
proportion of this sample that would have achieved the old standard (95% of all calls within
14 minutes ) is 98.1%.
The above give the response times according to the dispatcher's category, as used in
performance standards. However, this is only used as a proxy measure for the critically ill.
A more reliable measure of the response in relation to clinical need is to look at the figures
according to the expert assessment of urgency of ambulance requireme nt. This
81
demonstrated that only 67.0-69.3% of expert "gold standard" category “A” cases were dealt
with in 8 minutes and 98.1-98.4% of expert category “B” & “C” cases were responded to in
less than 14 minutes. (Ranges reflect experts “B” and “C” opinions of categorisation).
Table 6.19. Response times by CBD category.
6.19a response times by CBD
Category A Category B Category C N = %
< 8 mins 338 623 138 1099 69.6
8<=14 mins 114 264 72 450 28.5
>14 mins 7 18 4 29 1.8
TOTAL 459 905 214 1578
χ 2=6.6 (4df), p = NS. The response times do not show any significant variation by CBD
category.
6.19 b percentage achieving new 2001 standards
CBD category Actual Target
Category A 73.6% 75% in 8 minutes
Category B 98.0% 95% in 14 minutes
Category C 98.1% 95% in 14 minutes
Overall within new standards 90.9%
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6.14 Limitations
This study relies on various assessments to determine the need for a category “A” response.
No single measure is perfect. By combining expert opinion, physiological abnormality,
interventions undertaken and outcome measures, this study aims to produce a full view of
the factors that build up a picture of accuracy and safety of CBD.
Many of the measures used in this study relate to the state of the patient at a time after the
prioritisation had taken place, including at the time the ambulance personnel assessed the
patient after their arrival and at the accident and emergency department. It could be argued
that the patient’s condition had changed since the time of the dispatcher’s assessment. This
is not believed to be a significant limitation as CBD must be able to predict any
deterioration that may occur in a patient if they did not receive an 8 minute response.
Expert opinion is a subjective measure and therefore open to individual variation. The
experts were chosen for their knowledge in the field of emergency care.
Interventions that were undertaken either at scene or immediately on arrival were used as a
proxy measure for urgency of care. Some interventions may have been inappropriate.
However, in the majority of cases, one would expect that there was some cause for concern
that should have been detected by the dispatcher. Physiological parameters would be
expected to be more reliable indicators of severity of illness, although the variation from an
individual’s normal state can never be assessed in a study such as this.
Outcome measures give an indication of the severity of the illness. However, the
prehospital state of the patient is only one factor. Outcome will also be affected by the
quality of care subsequently received, development of complications and progression of the
disease condition.
6.15. Discussion
6.15.1. THE EXPERTS The gold standard adopted in this study is the CBD coding by the expert when he has the
full information, including diagnosis. This standard best reflects the patient's actual needs
for their clinical condition. However, the variation between experts B and C demonstrates
83
that a true gold standard is not achievable using opinion since a true gold standard is not a
fixed point unaffected by external factors. It is acknowledged that the ambulance dispatcher
will never have this amount of information available. However, an absolutely safe system
would have no under-triage rate compared to the gold standard. An infinitely efficient
system would have no over-triage. Safety is the overriding consideration in establishing a
prioritisation system, so the aim of a prioritisation system must be to achieve a near zero
under-triage rate with as low as possible over -triage rate as a secondary factor.
Analysis of the triaging by the nurses compared to the experts “expected” category reveals
great variation (25% under-triage and 21% over-triage), but equally in both directions (line
16 of Table 6.9). When compared to the gold standard of final diagnosis, the nurses’
overestimate and underestimate was comparable with that of the experts’ in the same time
period. This initial sample demonstrated that no extra information was obtained by using a
nurse assessment. Hence expert opinion based on the information in the notes appears to be
as reliable as a nurse who is able to interview the patient and ambulance crew. This
suggests that the experts in this study had sufficient information to make their judgements,
compared to the nurse who could ask the patient directly. The nurse coding was therefore
not used after the first week as it added no extra information and because it may have
several inherent disadvantages:
• Poor compliance rate
• Inter-observer variability of nurses
• Variability in understanding of prehospital urgency.
Comparing the expert B “expected” and “on diagnosis” codes confirmed reliability (line 12,
Table 6.9). Only 1% of cases were under-triaged by him from the notes and subsequently
modified when the diagnosis was known. The figures demonstrate that expert B works as
would a near optimal system in that there was a low underestimate rate (1%) (only misses
1% serious cases). There was, however, a high over -triage rate (53%). This suggests that it
may be impossible to achieve any increase in efficiency without a decrease in safety.
Expert C is more varied in his categorisation but on more occasions over-triaging with an
under-triage rate of 9% relative to expert B and over-triaged rate of 36% was observed (line
14, table 6.9), when information, including diagnosis, was available. (Over -triage results in
a higher prioritisation). Expert C also had a higher under-triage rate compared to expert B
84
when their opinions on final diagnosis are compared against expert B's diagnosis from
notes information (lines 12 &13, table 6.9), the dispatchers code (lines 4&5, table 6.9) and
to the CBD system code on prehospital information (lines 9 & 10, table 6.9) or on accident
and emergency department information (lines 6 & 7, table 6.9). This may be due to a
different perspective as this expert was actively involved in prehospital care and therefore
more accustomed to dealing with the patients before a diagnosis was established. In the
scenario of uncertainty, it is best to over-triage and, therefore, to be safe rather than to save
on resources.
Expert C also demonstrated a highly reproducible opinion with a high kappa score. Expert
opinion inevitably gives a spectrum of views. It is therefore important that further analysis
includes both experts and that neither are individually considered to be the gold standard.
6.15.2. CATEGORISATION OF CASES
The dispatchers under -triage by 33 % and over-triage by 22% when compared to expert B
on similar information (line 3, fig.6.9). Over-triage is to be expected as dispatchers have
less information available to them than the experts. The observed under -triage rate reflects
a potential hazard to the patient and could be due to inadequate information via the
telephone, communication difficulty, poor performance by the dispatcher or because of the
failings of the CBD system. Lines 1 and 2 of table 6.9 demonstrate the performance of
dispatchers when compared to the CBD system used using either the prehospital
information or the information available in the accident and emergency department. It
demonstrates low rates of dispatcher under-triage (9% and 8%) but approximately one third
over-triage by dispatchers compared to strict adherence to CBD. This suggests that under-
triage is due to incorrect usage of the CBD system (reflecting dispatcher performance) or to
lack of information in only a small proportion of cases. It implies that it is the guidelines
that are causing the under -triage observed in the previous analysis.
Although the over-triage rate appears large, this is a safety margin. It may be possible to
obtain improvement by increasing the information obtained from callers rather than by
different use of the system. It is not known whether the extra information can be obtained
85
from the public. The qua lity of information currently obtained is studied in chapter 8.3. In
this study, trained ambulance personnel and hospital staff acquired the information for the
experts. The dispatcher, however, has to obtain this information from the person on the
telephone, without any visual prompt. The minimal difference of 2% under-triage and 2%
over-triage between the CBD system results when using the prehospital information or the
accident and emergency department notes, confirms that equally reliable information can be
obtained from the scene by the ambulance crew in a face-to-face situation. This does not
however address the problem with obtaining information via telephone rather than direct
observation. It is important to note that this only relates to information required by the
current CBD system, not related to the more detailed information required to make a
definitive diagnosis.
Whereas expert A, using strictly CBD guidelines, had a high under -triage rate (45%)
compared to expert B “notes info” (line 5, table 6.9), the dispatchers only had a 33% under-
triage rate (line3, table 6.9). This implies that the CBD system is the cause of the majority
of under-triage cases. The same applies when comparing the under-triage of dispatchers
(10% - line 4, table 6.9) and A&E CBD (13% - line 6, table 6.9) with expert B “on
diagnosis” code. The difference is less marked when compared to expert C - dispatchers
(21% - line5, Figure6.9) and expert A using the CBD system (25% - line7, table 6.9). This
implies that the dispatchers are performing more accurately than would be expected by
strict adherence to CBD guidelines. A lower under-triage is mirrored by a higher over-
triage rate in all of the above categories. When compared to final diagnosis by expert B or
C, the dispatchers appear to have a higher over -triage rate than the CBD system (54% and
40% for dispatchers compared to 39% and 27% for CBD system - lines 4,5,6,7, table 6.9).
Hence in this set, the dispatchers appear to upgrade the coding to a greater extent than they
downgrade it. Because of this disparity, it is only possible to conclude that safe practice is
being undertaken, The dispatchers are improving on the strict use of CBD system by using
their skills.
The improvement in dispatcher performance from expert B “notes info” (line 3, table 6.9)
to expert B “on diagnosis” (line 4, table 6.9), shows that many cases of under-triage are in
high risk patients which subsequently prove to be of less clinical significance. They were
apparently potentially serious but were subsequently shown to be less severe. This is also
associated with an increased safety margin, as shown by the increased over -triage. The
86
change in expert B's opinion between his assessment from information in the accident and
emergency department notes and the final diagnosis suggests that the over-triage of 53%
results from the lack of definitive diagnosis and having to assign a higher priority to a case
until the most serious diagnosis is excluded.
Cases under-triaged for their final diagnosis represent the failings of the system and a risk
to the patient. From this expert opinion, it is concluded that this risk is occurring in 10-20%
of cases with current use of CBD. It appears that this is mostly due to the CBD (UK)
guidelines rather than their implementation.
6.15.3QUALITATIVE CASE REVIEW
The error rate solely attributable to the dispatcher was 0.98%, this appears to be a low rate
but no comparative data is available. However, there are errors that are due to a
combination of dispatcher and system, so the best estimate of the true error rate is 8% (25
cases in 304). The dispatchers improved on the system in 3.9% of cases. This demonstrates
that the dispatchers are using the system, as designed, to guide their decision making, but
not to rule it. However, the danger of such a system is that this improvement rate is
dependant on individuals and their training.
The case review suggests that some individual codes should be changed and these are
summarised below with the rationale for the change.
• Fits of unknown origin (code 11B3) should be allocated as category “A” in case it is a fit
secondary to hypoxia, hypoperfusion or brain injury – a case of severe left ventricular
failure presented as a fit, two other fits of cardiac origin.
• Continuing fit should be added to the description of “fitting more than 5 minutes”
(11A2) or “unconscious” (11A1). Two cases were missed because they were coded
simply as fits. It is known that the public do not understand the term unconscious80 and
if the fit is still ongoing but less than 5 minutes, its course cannot be predicted.
• Weakness in a diabetic (9C2) should be presumed to be developing hypoglycaemia
unless it is of gradual onset - missed hypoglycaemic in a diabetic with recent onset
weakness.
• Code 9B1 (diabetic, decreased level of consciousness) is upgraded to Category “A” – a
patient with peritonitis who was labelled as diabetic with decreased conscious level.
87
Decreased conscious level in a diabetic is often a sinister sign (suggesting
hypoglycaemia, sepsis, diabetic ketoacidosis) and needs urgent attention.
• Code 22B3 (electrocution / electrical burns) upgraded to an “A” category, because of the
risk of cardiac arrhythmia.
• Falls over 10 feet (24B5) should be priority “A” because of the high risk of serious
injury
• 25C1 (bump or laceration from fall with no loss of consciousness) should exclude high
risk mechanisms of injury. The same applies to cuts, bumps and bruises (24C1 or 24C2)
• Road traffic accidents should be upgraded to “A” if there is insufficient information on
the patient in high risk accidents such as rollovers, persons trapped
6.15.4 STUDY OF OUTCOMES
Those with physiological abnormalities that are potentially life-threatening are only
detected and classified as category “A” in 45-69% of cases. Those who are unconscious are
no more likely to receive a category “A” response than other patients. Those requiring an
urgent intervention are only coded as category “A” in 5-80% of cases. These measures all
reflect patients who could potentially come to harm from delay in their care. It is in this
measure that the highest failure rate of the system is seen. In many cases the use of
prioritisation did not even produce a trend towards those needing interventions being more
likely to receive a category “A”. No previous study has looked at this group of critically ill
patients in a separate analysis. Other studies have hidden this group in the much larger
numbers of well patients for whom time is unlikely to affect their outcome. It is this group
of patients who require early assistanc e that prioritisation systems are designed to help
when resources are limited and yet they will be frequently missed by the present use of the
CBD (UK) system.
Category “C” patients are those with less serious problems. Although none needed an ITU
admission from A&E, category “C” represented 1.1% of admissions to high dependency
areas, 15.5% of the admissions to hospital and 9.3% of the deaths. These figures all suggest
that category “C” contains a significant number of people who need hospital care and ma y
have serious illness. It would therefore not be safe to presume that category “C” equates
with minor illness without more detailed evaluation of the patient. However, it is not known
88
whether ambulance response time would affect the outcome, except in those suffering
cardiac arrest.
It is accepted that Category “A” will include many patients who are not critically ill or
injured as a safety margin. One quarter of all patients categorised “A” are subsequently
discharged from hospital. 6% of patients with category “A” have had symptoms for more
than 12 hours. Further research is required before any recommendations could be made
about including duration of complaint in the prioritisation system
6.15.5RESPONSE TIMES
It is not possible to determine whether the introduction of CBD has caused a change in
response times. Firstly, the categories did not exist before CBD, although they could be
retrospectively allocated. More importantly, other changes in the provision of the service
have accompanied the introduction of CBD within the West Midlands Ambulance Service.
These include the provision of first responders, who are individuals not in an ambulance
who respond to an incident to administer first aid. They include trained members of the
public, motorcycle paramedics or paramedics in cars. There was also a change in the
method of working whereby ambulances were allocated to standby points. In this way the
ambulances are evenly spread over an area rather than clustered at ambulance stations.
This study has shown that there is no significant difference in response times between the
different CBD categories. In the UK the main aim of the introduction of the system was to
improve the response to the seriously ill in a resource limited environment. At present it
does not appear that resources are being focused on this issue. However, the old system had
only a 14 minute response, so the new system does mean that category “A” patients are
given an improved target. It is possible that the whole system has improved but not
specifically for category “A” patients. Since a paramedic responds to every case, CBD is
not used to determine level of response. If times have improved globally, it raises the
question of whether the prioritisation systems have benefited the ambulance services and
therefore the patient in their present usage or whether other changes have caused the
improvement.
89
6.16 Conclusions
In this study, dispatchers appear to follow CBD guidelines accurately, except in some cases
where they override the system and therefore apparently over-triage. This over -triage
appears to be beneficial by improving the accuracy. It may be that they are using their
experience and concern that a case is more serious than CBD suggests to manipulate the
coding to give the priorit isation they want.
Under-triage appears to result mainly from the system rather than the dispatchers. Some of
the under-triage is in patients with a high risk story but whose final diagnosis reveals that
they were not at risk. Hence it is not of clinical significance. However, 10.3-21.3% of
patients appear to be put at clinical risk by undertriaging. Their diagnosis and clinical
condition suggest the need for earlier attention than that allocated by the prioritisation of
CBD.
There are significant numbers of patients who are physiologically unwell or who require
urgent medical interventions but who are not being classified as category “A”. Potential
spinal injuries are particularly poorly detected by CBD. Many with airway obstruction or
unconsciousness were not detected. This group of patients is studied further in chapter 7.
Equally, category “C” does not appear to reflect those who are well or could receive a non
urgent response, without them having a more detailed evaluation. The patients who could
be discharged home are studied in chapter 8.2.
Specific modifications highlighted by case review were suggested in the discussion which
may help decrease this risk.
At present the ambulance service does not appear to use the CBD categorisation system to
target those individuals with suspected serious illness or injury for a more rapid response.
The use of CBD as a resource allocation tool is studied further in chapter 8.4.
90
7. STUDY OF HOSPITAL ALERTS
7.1 Introduction
The initial expert opinion highlighted a cause for concern due to the poor level of agreement
with the CBD system. The literature review demonstrated that the system was not founded on
a strong evidence base and that there had been no rigorous evaluation of the system. The
outcome study has demonstrated an under-triage rate of 12.6% - 25.6% when comparing
actual dispatch prioritisation with expert opinion with knowledge of eventual diagnosis. The
actual system has a higher rate that is corrected by the intervention of the dispatcher. The
patient’s early or late outcome does not seem to relate accurately to their CBD coding. The
outcome study also highlighted that certain seriously ill patients, especially diabetics, those
having fits, suffering trauma, with airway obstruction, with potential spinal injury and who
are unconscious may be at particular risk. This group of seriously ill or injured patients
requires study in more detail, looking at those patients whom the ambulance personnel on
scene believe to be critically ill.
An “alert” describes the situation where an ambulance crew requests that the hospital be
notified before their arrival, because they perceive that the patient's clinical condition requires
immediate attention on arrival at hospital or a special response (for example, trauma team).
Exact criteria may vary between hospitals and between ambulance services. It follows,
therefore, that all such patients should have been categorised as “A” by the dispatching
system, providing the crew has made an accurate clinical assessment. Comparison of cases
classified as alerts with the ambulance prioritisation of these patients, should therefore, serve
as a method of assessing the effectiveness of the dispatch system in detecting the most
critically ill or injured patient. A predictive element is needed in the system, by which any
deterioration between telephoning for an ambulance and its arrival could be predicted from
the interrogation. A failure to obtain such information should result in a high priority as a fail-
safe mechanism.
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This study aimed to determine whether Criteria Based Dispatch accurately categorised 999
calls and allocated an “A” priority for those patients that was later followed by an “alert”
message to the hospital, from the ambulance crew.
7.2 Methods
The study population was identified by a search of the West Midlands Ambulance Service
Ambulance Emergency Control computer for the text word “alert$” (not case dependant) in
any field of the Ambulance Control Database. All cases in the one week study period 24/4/97
– 30/4/97) were included in the analysis. “Alert$” signifies both the word “alert” and any
word with “alert” as its first 5 letters. Any request for a hospital to be alerted should have two
database entries – first, a note of the request to alert and, second, the fact that the hospital had
been alerted recorded on the Ambulance Control Database. The printout for each case was
reviewed and cases where the word “alert” was detected in another context, for example,
bomb alert, were discarded. Information from the ambulance database is demonstrated in
table 7.1.
Table 7.1. Information from ambulance database for alerts study
Field in database Contents
Call identity Individual ID number, date and time
Location of caller Tel. No. and location as given by caller
Clinical details Details as given by caller
CBD coding
Timings of response Time of call, ambulance dispatch, ambulance arrival at scene, departure from scene, arrival at hospital
Details of ambulance/units responded Both number and type of response
Additional notes Any messages from crew for example, transcript of radio messages
Alert messages
Confirmation when informing hospital
Pronouncement of death details
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Patient report forms were obtained from the ambulance training centre, where a copy of all
the report forms are stored.
The dispatch category and ambulance patient report forms were reviewed by the author to
determine the clinical grounds for the crew alerting the hospital. Physiological parameters
(pulse, respiratory rate, systolic blood pressure and Glasgow Coma score), as well as AVPU
consciousness scale81 were recorded. Revised Trauma Scores82 were calculated, as was the
Shock Index83. These scores enable identification of the severity of the injury and therefore
cases in this study that may not have warranted an alert can be identified. Other cases could
be confirmed as critically ill on clinical grounds, as shown in table 7.2
Table 7.2. Criteria for determining critical illness on clinical grounds
Type of abnormality Abnormal result
Airway Obstruction Any
Breathing / Respiratory Distress Respiratory Rate > 29, Oxygen Saturation ≥ 90%
Circulatory Collapse BP < 90 systolic, Pulse > 140 or < 40
Burns needing fluid resuscitation
Actual blood loss > 1500 mls
Disability Unconscious with risk to airway (GCS<8, or responding to pain only)
Fitting continuously Any
Massive uncontrolled bleeding Any
All cases that had been classified as Category “B” or “C” were individually reviewed.
Qualitative analysis of all the records relating to under-triage cases was undertaken to
determine potential reasons for the under-triage. All cases had retrospective categorisation
using CBD (UK) guidelines with the information available as part of this analysis. This
review assessed whether the case was a critical illness or injury and the reason for
misclassification was deduced from the information available.
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T-tests, Analysis of Variance (ANOVA) and the non-parametric equivalent (Kruskal-Wallis)
tests were used as appropriate. After this analysis, modelling was undertaken to determine the
effects of the recommended changes and how such changes could be instituted.
7.3 Results
During the seven day study period, West Midlands Ambulance Service dealt with a total of
3,004 emergency 999 calls, relating to 2,563 incide nts. 3,023 operational units (including
ambulances, motorcycles, fast response units, and medical teams) responded to these
incidents. 104 cases were identified as resulting in a hospital “alert” call. All occurred in both
locations on the database, implying no missed cases. The distributions of diagnoses by
alerting ambulance crews and by dispatcher's CBD prioritisation code are shown in Table 7.3.
Table 7.3. Distribution of diagnoses by the alerting ambulance crew and the dispatcher’s
CBD classification.
Diagnosis by alerting crew
No of cases
% of total cases
Classified A
% A
Classified B
% B2
Classified C
% C
Unclass-ified..
% Uncl.
Cardiac Arrest 37 36 34 92 3 8 Cardiac symptoms
6 6 3 50 2 33 1 17
Trauma 17 16 9 52 6 (21) 35 1 6 1 6 Burns 2 2 0 0 2 100 ?CVA 3 3 2 66 1 33 Diff Breathing 18 17 10 56 7 (51) 39 1 6 Overdose 7 7 5 71 1 14 1 14 Fits 8 8 6 75 1 13 1 13 Non-traumatic Blood loss
4 4 0 0 4 100
Hypoglycaemia 1 1 1 100 0 0 Others 1 1 0 0 1(11) 100 TOT AL 104 100 70 67 28 (81) 27 1 1 5 5 1 Figures in brackets indicate the maximum number where ambulance observations did not justify the alert and
there was a possibility that these cases did not need to be an alert.
Eight cases (indicated by bracketed num bers in Table 7.3) were identified where the
information available did not demonstrate critical illness. The comparison between chief
complaints ascribed by the dispatcher and by the on scene ambulance crew is demonstrated in
Table 7.4.
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Table 7.4. Compa rison of dispatcher and ambulance crew diagnosis.
CBD chief complaint by dispatcher
No Ambulance Diagnosis No.
Bleeding 1 Blood loss 1 Difficulty in Breathing 18 Difficulty Breathing 13 Cardiac Arrest 4 Post ictal 1 Cardiac arrest 5 Cardiac Arrest 5 Chest pain 10 Chest Pain 4 Difficulty breathing 1 Cardiac arrest 5 Diabetic emergency 1 Diabetic emergency 1 Fits 8 Fits 4 Stroke 1 Cardiac Arrest 3 Gynaecological 1 PV Bleed 1 Overdose 3 Overdose 3 Stroke/CVA 3 Stroke 1 Difficulty Breathing 1 Fitting 1 Unconscious 24 Cardiac arrest 16 Head Injury 2 Stroke 1 Overdose 3 Difficulty breathing 1 Arrthymia 1 Assault 1 Stabbing 1 Burn 2 Burn 2 Fall 4 Fall 2 Arrhythmia 1 Internal bleeding 1 Head injury 3 Head Injury 3 RTA 8 RTA 8 Child fits 2 Child fits 2 Child trauma 1 Child trauma 1 Sick/unknown 9 Cardiac arrest 4 Bleeding 1 Difficulty Breathing 2 Overdose 1 Unknown 1 Total 104 104
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7.3.1. APPROPRIATENESS OF ALERTS
It was judged that in a maximum of eight cases (indicated by bracketed numbers in table 7.3)
the ambulance crew may have overestimated the severity and the case may not have
warranted an “alert”. Two of these cases were trauma, 5 were difficulty in breathing, and the
other was not classified.
• One of the trauma cases was a head injury who was fully conscious with normal
physiology.
• Four of the cases with shortness of breath had normal physiological parameters
• One case of shortness of breath had insufficient data to assess.
• One trauma case and one unclassified case had insufficient data to assess the reason for
the “alert”.
If all alerts were considered appropriate, 27% (29 of 104 cases) were assigned to priority “B”
or “C”. 8 could not be confirmed as critically ill. If those cases that could not be confirmed as
critically ill by expert review are excluded, then 19% (21 of 104 cases) were inappropriately
assigned to priority “B” or “C”.
7.3.2 Comparisons of alerts with other severity scores
Of the 104 patients studied, 101 had a level of consciousness recorded according to the AVPU
scale. 25 were alert, 9 responded to vocal command, 12 to pain only and 55 were
unresponsive. Table 7.5 demonstrates the categorisation between conscious level measured on
the AVPU scale and CBD (UK) priority group. Eleven (52%) of 21 under-triaged cases were
either unresponsive or responding only to pain but were not assigned an unconscious code by
the dispatcher.
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Table 7.5. Conscious level on AVPU scale vs. CBD category.
AVPU code CBD
“A”
CBD
“B”
CBD
“C”
No CBD code
Total
A = Alert 12 12 0 1 25
V = Respond to voice
5 4 0 0 9
P = Respond to pain only
5 5 0 2 12
U = Unresponsive
47 5 1 2 55
AVPU
not known
1 2 3
Total 70 28 1 5 104
The Revised Trauma Scores (RTS) and the Glasgow Coma Scales (GCS) were assessed for
the 17 trauma patients There was no significant difference between Category “A” (mean score
7.8) and Categories “B” and “C” (mean score 6.9) patients with respect to RTS (p =0.105,
Kruskall-Wallis Test) (see table 7.6).. The differences in GCS (mean scores: Category “A” =
14.4, “B” = 12.9, “C” = 5.0) between the CBD (UK) categories were however statistically
significant (p<0.005, ANOVA) (see table 7.7). The distribution of GCS is opposite to what is
expected, partly due to the small numbers and the bias of sampling only alert cases.. The
category c patient was initially fully conscious and then deteriorated after the 99 call such that
his GCS was 5 when the ambulance crew arrived. In the road traffic accident (RTA)
subgroup (n =8), three of the four misclassified cases also had a GCS < 12 (AVPU was P in
one case and V in the other two). the fourth had insufficient information to conclude the
reason for under-triage.
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Table 7.6. The Revised Trauma Scores (RTS) for trauma patients.
CBD category n =
Range mean Revised Trauma
Score
Category “A” 4 7.8* 7.8
Category “B” 8 3.9 - 7.8 6.9
Category “C” 0 - -
* RTS equal in all cases
Table 7.7. Glasgow Coma Scale of trauma patients.
CBD category
mean GCS No. of cases
A 14.4 5 B 12.9 10 C 5.0 1
The four cases of haemorrhage had Shock Indices calculated. The Shock Indices were all
greater than 0.83 (range 1.14 – 2.75). A Shock Index above 0.83 is associated with a high risk
of transfusion and ITU admission2,84.
7.3.4 QUALITATIVE C ASE REVIEW FOR CAUSE OF UNDER-TRIAGE
There were twenty cases of under-triage, some had more than one reason why they should
have been categorised as “A”.
• Three cases where fitting was a presenting symptom of cardiac arrest but coded as a fit
(code 11B3)
• The two cardiac related problems in older people both had the same cause of under-triage.
A fall from a medical cause (24C3) and a medical collapse (19B3) were classified by the
event witnessed rather than the medical cause.
• One stroke case resulted in under-triage because it presented as a fit which had stopped
(11B5) but the patient was still deeply unconscious (GCS=6).
• One fit was misclassified as a “fit of unknown history” rather than a continuing fit.
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• One overdose, out of seven in this study, was misclassified and was only responding to
pain and therefore should have been classified as unconscious (15A1), but had been
classified as 15B3 (intentional/ accidental drug overdose).
• Two burns cases were under -triaged because of an underestimation of the extent of the
burn.
• Four cases of severe bleeding had a “B” category allocated
• Head injuries were under-triaged because CBD does not relate to the accepted guidelines
on the management of head injury85.
• In the RTA subgroup, the correctly classified cases were all because the patient was
unconscious. All others RTA alerts were Category “B”. Three of the four cases
misclassified had a GCS <12, (AVPU was P in one case and V in the other two, indicating
a significantly decreased level of consciousness; the fourth was alert). The fourth error
appears to be related to using “mechanism of injury” rather than “conscious level” as the
prime-sorting field.
• One fall was classified as a “B” correctly according to CBD, which classifies a fall from
over 20 ft. as a Category “B”.
• Minor bump on head, subsequently deteriorated, no identifiable risk factor was found.
• There were eighteen cases of difficulty in breathing. Assessment of their need for an
“alert” call was difficult, as ability to talk, respiratory rate and oxygen saturation were not
recorded in most cases.
A full list of the resulting recommendations is contained in Appendix 10.
7.3.4 EFFECT OF RECOMMENDATIONS
When these recommendations for changes in the CBD system and dispatcher training were
reapplied to the original data it resulted in a total of 25 of the 28 (89.2%) miscodings being
corrected to a category “A”. The other three cases were all cases of difficulty in breathing
where it could not be established that the patient was critically ill.
Fifteen (53.6%) of the se corrections could have been achieved either by a change in the
training of dispatchers or a change in the coding system. Ten (35.7%)could only have been
brought about by changes in the coding system.
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7.4 Limitations of this study
All cases identified in the study period were included. Although the sample of cases is small,
particularly when individual complaints are analysed, the apparently high degree of under-
prioritisation in a system in active use make this small study important. A larger multi-
ambulance service study is needed to determine under-triage rates with greater precision and
to ensure generalisability.
The assessment of severity of most illness is subjective. The only scoring systems that exist
and are applicable to the prehospital field are those relating to trauma and haemorrhage. In the
other cases the author undertook individual assessment of the need for emergency
intervention. This study has excluded all “alert” cases that may not have had critical illness or
injury.
Only those cases where the ambulance services “alert” the receiving accident and emergency
department have been studied. This enables concentration on those cases needing urgent
intervention. These are the group who could most benefit from the improved response times
of Category “A”. This alerts methodology is informative because it is the critically ill who are
most at risk from a prioritisation system.
If a patient deteriorates after the 999 call, but before arrival of the crew, this will appear as a
failure of the system. An effective prioritisation system must have this predictive element as
well as simple assessment at the time of a 999 call.
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7.5 Discussion
The methodology of the two studies previously undertaken in the UK was similar but did not
specifically look at the most critically ill. The Sheffield31 study reported that only 4 (1%)
cases in 571 had serious under-prioritisation, as judged by expert assessment. The London
study86 quoted a 2% under-triage rate but also stated that only 2 of these 15 cases could not be
resolved by quality improvement. The outcome study in this thesis also highlighted that
certain seriously ill patients, especially diabetics, those having fits, those suffering trauma,
those with airway obstruction, potential spinal injury and who are unconscious may be at
particular risk. This alerts study, alarmingly, suggests at least a 20% under-triage rate.
CBD (UK) appears to fail to detect the immediate emergency in 20-28% of 999 calls which
result in a hospital “alert” call. Improvements must be made to the CBD (UK) system to
reduce the level of under-triage. Although only one case was classified as priority “C", this
highlights the potential danger of a non-ambulance response to the conscious head injury,
because of the well recognised delayed deterioration that may occur with an intra-cranial
haematoma.
The difference in chief complaint as described by the dispatcher and the on scene ambulance
crew is marked in several groups. The difficulty in detecting cardiac arrest over the telephone
is illustrated by it presenting in several different dispatchers' chief complaint categories. This
may reflect difficulty in detection, poor observation by the caller or progression of the
condition between 999 call and arrival of the ambulance. Early cardio-pulmonary
resuscitation is an intervention demonstrated to improve survival87. Nineteen (51%) of the
patients in this study who presented as cardiac arrest or possible apnoea would have received
advice over the telephone on cardio-pulmonary resuscitation (CPR). The remaining 18 would
have had no CPR advice given. Only three of these latter cases were due to failure to
recognise a symptom (fitting) related to cardiac arrest. The other cases were due to the cardiac
arrest occurring after the call.
Ambulance services undertaking prioritisation of 999 calls should undertake audit to study the
categorisation of all alert cases and carefully investigate any that have not been assigned to
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Category “A”. This would enable improvement of the system and monitoring of staff
performance without creating an excessive auditing workload.
At present, the increase in over-triage or resource requirements that the recommendations of
this study may produce cannot be predicted. Ambulance crews may have a lower threshold for
alerting because their individual patient’s welfare is their sole concern. However the
prioritisation system has to meet the needs of the population as a whole. The prioritisation
system does, however, have to have a high sensitivity for critical cases. Only in this way can
appropriate emergency care be delivered to those with time critical illness or injury. Low
sensitivity will cause adverse clinical outcomes in the most seriously ill. Low specificity of
Category “A” may mean poor use of resources but does not cause any clinical harm. A review
of the United Kingdom CBD guidelines to increase sensitivity should be undertaken, whilst
further research looks at increasing specificity.
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8.1. Was CBD changed before use in the UK?
8.1.1. Introduction
This thesis has highlighted some major problems with CBD. The initial expert opinion
highlighted a cause for concern due to the poor level of agreement with the CBD system. The
literature review demonstrated that the system was not founded on a strong evidence base and
that there had been no rigorous evaluation of the system. The outcome study has demonstrated
an under -triage rate of 12.6% - 25.6% when comparing actual dispatch prioritisation with
expert opinion with knowle dge of eventual diagnosis. It also highlighted that certain seriously
ill patients, especially diabetics, those having fits, those suffering trauma, those with airway
obstruction, potential spinal injury and who are unconscious may be at particular risk. The
particular areas of concern demonstrated by the alerts study are the failure to recognise
cardiac arrests. The miscodings are often related to fits, severe bleeding, unconsciousness,
falls/faints and the use of mechanism of injury rather than clinical state. This part of the study
aims to determine if these specific areas of error may have been caused by the process of
change when CBD was adopted in the UK.
The process whereby the CBD system used in Seattle was modified to the format introduced
in the West Midlands in April 1997 has been described in chapter 4.2. Part of this process was
to reflect the change in the use of CBD. In America it is used to determine the level of
response for example, whether to send a technician or paramedic. In the UK its main objective
is to determine the speed of response.
The objective of this study is to delineate these changes and determine how many clinical
conditions have been promoted and how many demoted for their prioritisation.
8.1.2 Methods
Copies of the CBD guidelines in use in Seattle at the time of the UK adoption of CBD and the
present UK system were manually compared. The wording of the code description was
103
checked to ensure that the clinical description was not changed. All American and UK codes
were entered on a database and then merged. This enabled comparison of the coding of
identical medical conditions.
8.1.3. Results - The Changes
No descriptions associated with codes had been changed. Direct comparison was therefore
possible. Children under two years had been separated in the UK system to form a separate
group with all codes given a category “A” response. The UK system had also created a new
category (Group 20 -miscellaneous) to cover incidents where clinical details may not be
available (for example, bomb alert, fire alarm). The changes in coding are shown in Table
8.1.1.
Table 8.1.1. The changes in coding of CBD when imported into UK.
Chief complaint Description US Code*
UK Code*
March 1997
Comments
1. Abdominal/Back Pain
Lower abdo pain female 12 to 50 years with fainting and dizziness
1A3 1B1
Vomiting red blood 1A4 1B2 2. Allergic reaction NO
CHANGES 3. Animal Bites Uncontrolled haemorrhage 3A2 3B1 Severe bites to face and/or
neck 3A4 3B2
Bite from poisonous animal
3A5 3B3
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Table 8.1.1. (contd.) Chief complaint Description US
Code* UK Code*
March 1997
Comments
4. Bleeding Non trauma Multiple fainting episodes 4A2 4B1
Fainting or near fainting 4A3 4B2 Vomiting blood 4A4 4B3 Coughing up blood, more
than half a cup full 4A5 4B4
Lower abdo pain female 12 to 50 years if associated with dizziness or heavy vaginal bleeding
4A6 4B5
5. Breathing difficulty NO CHANGES
6. Cardiac Arrest NO CHANGES
7. Chest pain NO CHANGES
8. Choking NO CHANGES
9. Diabetic NO CHANGES
10. Environmental NO CHANGES
11. Fits/Convulsions Diabetic 11A4 11B1
Secondary to drug overdose
11A6 11B2
12. Gynaecology /Miscarriage
NO CHANGES
13. Headache Decreased conscious level 13A2 13B1 14. Mental/Emotional NO
CHANGES 15. Overdose/Poisoning Difficulty in swallowing 15A3 15B1
16. Pregnancy Delivery 16A4 16B1 17. Sick/unknown Multiple fainting episodes 17A2 17B1 18. Stroke/CVA NO
CHANGES 19. Unconscious Third party caller not with
patient 19B4 19A7 **
Multiple fainting episodes 19A2 19B1 20. Miscellaneous No US code
20
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Table 8.1.1. (contd.) Chief complaint Description US
Code* UK Code*
March 1997
Comments
21. Assault trauma Decreased level of consciousness
21A1 21B1
Uncontrolled bleeding 21A4 21B2 22. Burns Decreased conscious level 22A2 22B1
Burns to airway, nose, mouth
22A4 22B2
Electrocution/electrical burns.
22A6 22B3
23. Drowning Confirmed submerged more than 1 minute
23A3 23B1
24. Falls/Accidents Decreased level of consciousness
24A2 24B1
Amputation above fingers or toes
24A5 24B2
Patient paralysed 24A6 24B3
Uncontrolled bleeding 24A7 24B4 Fall more than 10 feet 24A8 24B5
25. Neurological/head injury
Decreased level of consciousness
25A3 25B1
Fall more than 10 feet 25A5 25B2
26. Road traffic accident
Decreased conscious level 26A2 26B1
Confirmed or unknown injuries with the following mechanism-
Vehicle Vs immovable object
26A3 26B2
Vehicle Vs vehicle (head on/side on)
26A3 26B3
Vehicle Vs Pedestrian 26A3 26B4
Vehicle. Vs motorcyclist 26A3 26B5 Victims trapped/ejected 26A3 26B6
Multiple vehicle/casualty accident.
26A3 26B7
27. Child under 2 All No US code 20
All cases Category
“A”
*The middle letter denotes the prioritisation letter ** Upgraded in UK system
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In only one case was the American code upgraded. Unconscious patients reported by a third
party caller were assigned a category “B” in the American system and an “A” in the UK
system. Every instance of “uncontrolled haemorrhage” except nosebleed was downgraded.
However, decreased conscious level is consistently a Category “B” in the UK system whereas
it is variable in the US. See table 8.1.2.
Table 8.1.2. Decreased conscious level coding in UK and US.
Chief complaint US code UK code
Diabetic 9B1 9B1
Headache 13A2 13B1
Overdose 15B1 15B2
Sick/Unknown 17B1 17B2
Stroke/CVA 18B1 18B1
Assault 21A3 21B1
Burns 22A2 22B1
Fall/Accident 24A2 24B1
Neuro/head injury 25A3 25B1
RTA 26A2 26B1
Child under 2 NO SPECIFIC CODE 27A
One area of the changes (gynaecological bleeding) also produced some anomalous coding, so
that the same condition had different priorities according to which chief complaint was used,
as shown in table 8.1.3.
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Table 8.1.3. Variation in bleeding code according to presenting complaint.
BLEEDING
UK
US GYNAECOLOGY
UK & US 4B1 4A2 Multiple fainting episodes
12A2 Vaginal bleeding with fainting
4B2 4A3 Fainting or near fainting when sitting up
12A3 Fainting or near fainting when sitting up
4B5 4A4 Lower abdo pain female 12-50 years if associated with dizziness/ fainting or heavy vaginal bleeding
12A5 Lower abdo pain 12-50 years if associated with dizziness/ fainting or heavy vaginal bleeding
Many of the areas of concern that have been determined in the outcome study and the alerts
study could potentially have been prevented by not changing the American system of CBD
when it was adopted in the UK.
8.1.4. Resource implications of changes
As all but one of the changes are from “A” to “B”, the modifications have decreased the
resource demand on the UK ambulance services by decreasing those cases needing the most
rapid response. To ensure rapid response to Category “A” patients, some ambulance services
are now using first responders. These are an additional resource because they are unable to
convey a patient, they simply start treatment and then hand over care to the ambulance crew
with a traditional ambulance, or accompany the patient in that ambulance (and have to
retrieve their vehicle later). Hence the financial implications of Category “A” cases over
Category “B” are significant.
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8.2 Patients not transported from the scene
8.2.1. Introduction
Most of the earlier work in this thesis has concentrated on the ability of CBD to detect the
seriously ill and injured. By categorising patients, CBD can also potentially be used to
identify those with lesser needs. It has been suggested that CBD can be used to detect those
who do not require an ambulance response. If certain cases could be diverted to other sources
of care, then the existing ambulance resource could be used more effectively. The outcome
study has demonstrated that patients initially categorised as category “C” are often in need of
monitoring in the ambulance or require a prehospital intervention, although they are rarely
physiologically disturbed. 10% of all admissions and 9% of deaths are categorised “C”. It is
therefore already apparent that it not safe to automatically state that category “C” patients are
safe to be transferred directly to another source of care. This study looks at those ambulance
calls that did not result in transport to hospital as an indicator of where resources could be
saved.
8.2.2. Objectives
there are two objectives to this study:
1. To determine the reasons for non-transport of 999 call patients.
2. To assist in determining whether CBD can be used to determine which cases do not
require ambulance transport.
8.2.3. Methodology
The emergency control centre database for West Midlands Ambulance Service NHS Trust
was searched for a one week period (01 Sept 1998 - 07 Sept 1998) for all cases where an
ambulance did not transport a patient to hospital following a 999 emergency ambulance call.
This week was chosen as being mid point of the outcome study but one year later, so that
seasonal effects should be similar, to make data comparable. Duplicate cases were excluded
from analysis by comparison of time/date and incident location.
109
The reason for non-transport is recorded in the database by the ambulance control room staff
as free text. This was classified according to a coding system previously developed and
validated in a 100 patient pilot 88. The reasons included were both clinical or operational. The
codes for the reason that a 999 call did not result in someone being transported are
summarised in table 8.2.1. Most of the groups are self-explanatory. The psychiatric group
included only those where the person was not transported to hospital but some would have
had the involvement of a community psychiatric team. Deceased indicates the ambulance
crews diagnosis, it does not indicate the opinion of the person calling 999.
The CBD(UK) code was also noted for each case, as was the time and date of the 999 call.
Analysis was undertaken to determine the extent of the problem of non-transport and to
determine if CBD can be used to predict those cases not requiring transport. Specific analysis
of CBD category “A” cases was undertaken as this may reflect a resource wastage, attempting
to respond within 8 minutes to cases that eventually did not need an ambulance to transport
them. The distribution of CND categories was compared with the distribution in the outcome
study ( chapter 6).
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Table 8.2.1. Coding of reason for non-removal.
Code No. Non-Removal Reason
1 Auto Fire Alarm - whether ambulance attended or not
2 Asthma
3 Hoax and malicious calls
4 Psychiatric
5 Minor medical / patient recovered, including fits
6 Social problems, including elderly / disabled patients needing lifting back into bed / wheelchair
domestic incidents 7 Intoxicated only
8 Violent
9 No injuries, patient checked by crew (or police)
10 Diabetic, recovered after treatment by self or crew
11 Crew or control requested GP / midwife / social worker visit
12 Patient deceased
13 Refused treatment
14 Smoke detector, no voice contact. False alarm
15 Duplicate cases
16 Patient using other transport to hospital
17 No sign of incident / Patient left scene of incident
18 Patient / caller changed mind - decided ambulance not required after all
19 Case assigned to other service - fire, police, other ambulance service
20 Airport alert - plane landed safely, crew stood down
21 False alarm, good intent
22 Police taken charge at scene
23 Patient will visit own GP later
24 Doctor already in attendance stood crew down.
25 Caller cleared at start of call and control unable to ring back or, call connected / made in error to wrong service
28 conveyed home
99 Other - no code
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8.2.3. Results
In the study period (01-07 September 1998) West Midlands Ambulance Service NHS Trust
Emergency Control Centre dealt with 4767 999 calls. Of these, 1332 calls, relating to 1066
individual incidents, did not require anybody to be transported to a healthcare provider.
Therefore, 27.9% (1332/4767) of all 999 calls received in the study period did not result in the
transport of a patient to hospital.
There was some variation by day of week. As shown in figure 8.2.1, there is a rise in the
proportion of 999 calls resulting in non-transport through the week with a maximum reached
on Friday and then declining over the weekend. There was marked variation by time of day,
as shown in figure 8.2.2, with an apparent bimodal distribution with peaks of non-transport
cases at 13.00 hrs. and 22.00 hrs. There does not appear to be any difference in the
distribution during the day between the category “A” cases and all cases studied together. The
variation in numbers of non-transported cases by time of day reflects the variation of total
number of 999 calls.
Figure 8.2.1. Variation of non-transported 999 calls with day of week.
% of non transported cases by day of the week
27.0% 28.0% 28.0%
32.4%
35.6%33.2%
31.1%
0%
10%
20%
30%
40%
Monday
Tuesd
ay
Wedne
sday
Thurs
day Friday
Saturd
aySu
nday
112
0.0%
1.0%
2.0%
3.0%
4.0%
5.0%
6.0%
7.0%
8.0%
9.0%
10.0%
0 1 2 3 4 5 6 7 8 9 10 1112 13 14 15 16 17 18 19 20 21 22 23
Hour ofday
%
of d
aily
tota
l
all nontransport
Category A non-transport
all 999cases
Figure 8.2.2. Variation of non-transported 999 calls with time of day.
The CBD coding of those not transported was category “A” for 196 calls (18.4%), category
“B” for 533 calls (31.5%) and category “C” for 336 calls (50%), compared to the distribution
from the outcome study of 28.65% “A”, 59.2% “B” and 12.1% “C”. (see figure 8.2.3).
A18.4%
B50.0%
C31.5%
Not transported Outcome study
Figure 8.2.3. Non transport by CBD code.
The reasons for non transport by CBD category are shown in Figure 8.2.4. The categories
have been divided according to potential cause and these are shown in Figure 8.2.5. 400 of t
the 1066 cases studied (37.5%) were considered to be due to unnecessary calls. 109 (10.2%)
were due to a hoax call, in 57 (5.3%) cases there was no sign of an incident, 29 (2.7%) had
used other transport by the time the ambulance had arrived, 33 (3.1%) had changed their mind
A28.7%
B59.2%
C12.1%
113
about needing an ambulance, 153 (14.4%) refused treatment when the ambulance arrived and
19 (1.8%) were caller errors.
No. cases not transported
0
20
40
60
80
100
120
140
160
Hoax
Refus
ed trea
tment
Other tra
nsport
used
No sign
of inc
ident
Chang
ed mind
Caller e
rror
Auto F
ire Ala
rm
Smoke
detec
tor
Airpo
rt alert
False
alarm
, good
inten
tPs
ychiatr
ic
Socia
l prob
lems
Intoxica
ted on
ly Violen
t
Other ca
rer re
q
Assig
ned to
other s
ervice
Police
taken
charge As
thma
Minor m
edica
l
No injurie
s
Diabetic
, recov
ered
Visit G
P later
Dr in att
enda
nce
Conve
yed ho
me
Decea
sed
Other - n
o code
category A category B category C
Figure 8.2.4. Total cases not transported.
114
Deceased3.5%
Other1.3%
Standby 10.9%
Other carerrequired28.4%
Assessed/Treated 17.4% Hoax
etc.38.5%
Figure 8.2.5. Reasons for not requiring transport.
303 (28.4%) of all the non transport cases were dealt with by other agencies. In 61 (5.7%)
cases the ambulance was called for social care (for example, to help someone back into bed)
and in 105 cases (9.8%) another carer was requested. An additional 17 (1.6%) cases required
the psychiatric team to attend. The police took charge in 32 cases (3.0%) and 40 (3.8%) were
assigned to other services before arrival of the ambulance. 43 (4.0%) were intoxicated and 5
(0.5%) were violent without evidence of illness or injury. These are detailed in figure 8.2.6.
Figure 8.2.6. Cases dealt with by another agency.
Assigned to other service
13%
Police taken charge11%
Social problems20%
Psychiatric6%
Intoxicated only14%
Violent2%
Other carer req34%
115
In 186 (17.4%) cases patients were medically assessed , treated and discharged from the
scene. Of these, 89 (8.3%) were after accidents when no injury was apparent, 10 (0.9%) were
diabetics and 8 (0.8%) were asthmatic s, who recovered after treatment.
116 (10.9%) cases were standby situations, accounted for by automatic fire alarms (99;9.3%),
smoke detectors (7; 0.7%), airport alerts (2; 0.2%) and 8 (0.8%) other cases. 37 (3.5%)
patients were not transported because they were certified dead at home and transported by
undertakers.
8.2.4. Discussion
Over a quarter of 999 incidents do not result in transport by ambulance. If these represent
cases where ambulance care was not needed, then this represents a large waste of resources.
The variation of non-transport calls by hour of day reflects the variation in the number of all
999 calls with time. There is an apparent increase in percentage of non transport calls during
the week with a peak on Friday. There is a recognised variation in use of ambulance services
by day of the week23 but the variation in non-transport cases has not been previously noted.
Analysis has not revealed any reason for this increase, in particular there is no apparent
increase in any one reason for non-transport. However, the study period was only one week
and conclusions cannot therefore be drawn from this.
The reasons for non-removal of a patient from the scene are highly variable. 18 (1.7%)
patients appear to represent the results of appropriate prehospital ambulance care including
asthmatics and diabetics in this group. This figure may be an underestimate as those refusing
transport may include some who have been treated and then recovered. Patients who had died
and in whom resuscitation was inappropriate accounted for 37 (3.5%) cases. They were all
appropriately categorised as “A” because the lack of need for resuscitation was not known
until assessment by the ambulance crew.
43 (3.2%) people were simply drunk. There may be difficulty in determining whether the
patient is drunk and safe, or unconscious with an airway risk. Nine of these cases were
reported to be unconscious or not breathing from the telephone information. Many of these
may be third party calls.
116
Those who refused treatment and had minor conditions or did not want treatment represent a
quarter (n =306 ; 28.7%) of the non-transport cases. Those with no injuries represented 8.3%
(n =89) of the study population. More study is needed to determine if these can be given
telephone advice rather than requiring an ambulance. These cases may result from third party
callers with little access to the patient, possible someone passing a road accident and calling
an ambulance on their mobile phone.
The GP cases were all cases where a GP had suggested that the caller contact 999 but the
ambulance crew thought hospital care was not needed. This study does not show whether the
GP subsequently referred the person to hospital and so the accuracy of the paramedics
decision cannot be verified. This group suggests the need for more integration of the
emergency primary care and ambulance services.
Social problems include those who have fallen from bed and need help back into bed and one
person who had wet the bed and needed the sheets changing. These 5.7% (n =61) of cases
were dealt with by the ambulance service because of a lack of another out of hours agency to
undertake this type of work.
The “violent” cases (n =5; 0.5%) were removed by the police because of danger to the
ambulance crew. They would have subsequently been assessed by a Forensic Medical
Examiner (police surgeon) if required.
Hoax calls are often cited as a major problem but only accounted for 10.2 % (n =102) of the
cases. Unnecessary calls for those refusing treatment (n =153, 14.4%) or leaving the scene (n
=29; 2.7%) may be deliberate misuse of the system but may be well meaning passers-by, who
fail to verify the situation before calling 999. Those who travel to hospital by other means,
after calling 999 could avoid this resource waste by informing the ambulance service of their
actions. Standby situations account for one in ten non-transports. Regular review is required
to see if they need an initial ambulance response. The majority are fire related and some
attendances may not be immediately necessary, for example, a fire at a hospital may not need
an ambulance response as ambulance may not be required even if a fire results.
Category “C” at present receives the same response as Category “B”. There are plans to
introduce telephone advice to this group and possible transfer to other agencies. Ideally, any
117
case that did not require paramedic treatment or transport to hospital should be classified as a
“C”.
Many more non-transport calls were prioritised as category “C” compared to all calls (50% v
12.1%) the system has the potential to halve the number of non-transport calls if category “C”
cases were dealt with in a different way. Proportions of category “A” & “B” cases in various
groups of those transported varies and is not isolated to specific diagnostic groups.
Those patients who are intoxicated present a difficult clinical scenario; they are at high risk of
having suffered an injury, their decreased conscious level means they are at high risk of
airway obstruction or aspiration of vomit and yet they are likely to refuse treatment or leave
the scene before the ambulance arrives. Nine patients in this series were reported to be not
breathing but were not transported, it mist be presumed that they were breathing but the caller
could not judge this. The difficulty in obtaining accurate information is reflected in the 24
different CBD codes that are ascribed to the 34 drunk patients believed to be breathing, the
most common code being the “other, unclassified” code (17B7). This illustrates the difficulty
of obtaining information from 999 calls and the need for over prioritisation to have a safe
system.
8.2.5. Conclusions
Although a quarter of 999 cases do not result in ambulance transport, many are for justifiable
reasons. These include patients who are successfully treated, those who cannot be confirmed
dead until arrival of the ambulance crew and potential disasters such as airport alerts.
Alcohol related incidents account for many non-transport cases. It is unlikely that this group
of non transport calls can be reduced. Social reasons for non-transport could be solved by
better access to emergency social services for emergency assistance.
Public information campaigns may help improve the quality of information received and
decrease the number of calls from incidents not requiring an ambulance. This may either be
by identifying more serious conditions or recognising cases more appropriate for other
services. If people have access to a vehicle they should be encouraged to use this for non life
118
threatening problems, rather than use an ambulance. Hoax calls continue to be a problem that
should be actively pursued.
At present CBD does not provide a useful tool for predicting calls where transport ma y not be
required. Although it has been shown that the category “C” calls could safely be directed to
NHS Direct89, the system classifies many cases subsequently not transported to higher
categories.
Category “C” has been shown to be a heterogeneous group. The outcome study demonstrates
that it has many patients who are ill, need admission to hospital and will die. This study
reveals that many who do not require transport are not classified as category “C”.
119
8.3 Are 999 callers in a position to give triage information and receive first aid advice?
8.3.1 Background
The studies in this thesis have already demonstrated that the CBD system has a high error
rate. This is partly compensated for by the experience and training of the dispatchers. Further
improvement may be achieved by reverting to the American version of CBD. It is unknown
how much of the error rate is due to the communications difficulties in obtaining information
over the phone from a person who is liable to be upset.
The ability of emergency ambulance services to obtain information from a caller is a key
element of their role. Difficulties in identifying the location to send the ambulance has been
eased by the introduction of automatic call tracing. However, prioritisation of emergency calls
and the delivery of first aid advice are dependent on good two-way communication between
caller and ambulance service call taker.
Previous studies have demonstrated that first aid advice can be successfully delivered over the
telephone 90, but these studies have not explored whether the location of the caller or language
difficulties may prevent these instructions being carried out. One study in China reported that
the majority of accidents were reported by passers-by who had little first aid knowledge and
did not want to be involved11. There has been no study carried out in the UK on the origin of
emergency ambulance calls or any communications problems experienced. The search
strategy for this data is shown in table 8.3.1.
Table 8.3.1. Search strategy on communications difficulties in 999 ambulance calls.
Databases searched: Medline, BIDS, CINAHL
Search Pattern
Ambulance Call
999 Emergency
Communication Ambulance
Dispatch
Combined with
Communication
120
8.3.2. Methods
A sample of 999 emergency ambulance calls arriving at the West Midlands Ambulance
Service emergency control room was studied. This sample was achieved by listening to
consecutive 999 calls taken by one position in the control room during two shifts spanning
08.00 to 00.00 hrs. on a Tuesday and Friday. Incoming calls are allocated to each position
according to availability of that line (call takers may have other calls to receive or make as
well as receiving 999 calls). The author listened to recordings of the calls, but was not
involved in the decision making or call taking. It was determined whether there were any
communication difficulties, the identity of the caller and their location in relation to the
patient. A communication difficulty was defined as any situation where the call taker had to
repeat a question or rephrase it more than once to obtain a reply or where an inappropriate
response was received on two or more occasions. They were classified as due to the following
causes:
• emotional / excitable
• inappropriate use of medical terms by the caller
• abusive
• not wanting to answer
• lack of comprehension
• child
• use of a non-English language.
The location of the caller was determined by comparing information provided by the call
tracing system with the location of the incident as described by the caller, by the conversation
content, by listening for the casualty in the background and by direct questioning of the caller.
This was then coded into one of the following categories:
a) present within talking distance of patient
b) can speak with and assess patient, but needs to leave the phone to do so
c) distant from patient, not in contact
d) only indirect contact possible, for example, via radio.
The caller’s relationship was usually apparent from the call content (for example, use of terms
such as “my husband”) but was asked by the call taker if not apparent.
121
95% confidence intervals have been calculated using the method described by Fleiss91.
8.3.3. Results
104 emergency (999 ) ambulance calls were monitored. Three calls were hoax calls, all of
which were from children, two of them used abusive language and did not give any location
or details, and one gave a false address and ended the call on requests for further details.
These cases are excluded from the further analysis. This provided a study population of 101
cases.
In 15 calls (14.9%, 95% CI 8.8-23.6), communications problems were experienced (table
8.3.2). Three cases were due to language difficulties. In one further case the initial caller
subsequently handed the phone to the patient who was able to communicate adequately. All
four of these cases involved callers in Indian subcontinent languages. In one case, no transfer
of information was possible. The location could be verified but further medical details could
not be obtained in two other cases and first aid advice could not be given in any of these four
cases. In five cases the emotional state of the caller was the key element to the difficulty.
However, in all cases, basic details could be obtained but first aid advice was declined or not
carried out. One call was from a person who was abusive when asked questions. In three
cases, the caller did not understand the questions which were being asked; another one used
medical terms inappropriately when answering and one call was a young child who did not
understand the questions. One call was on a mobile phone and the distortion made two-way
conversations extremely difficult.
122
Table 8.3.2. Communication Difficulties
Difficulty experienced No. of
cases1
% of total
calls
95% CI
Emotional/excitable 5 (0) 5.0 1.8-11.7
Misuse of medical terms 1 (0) 1.0 0.1-6.2
Abusive 1 (1) 1.0 0.1-6.2
Not wanting to answer, reason unknown 0 (0) 0 0
Lack of comprehension 3 (1) 3.0 0.8-9.1
Child 1 (0) 1.0 0.1-6.2
Line quality (mobile phone) 1 (0) 1.0 0.1-6.2
Language 3 (1) 3.0 0.8-9.1
TOTAL 159(3) 14.9 8.8-23.6 1The number of cases where communication difficulty was experienced is detailed in column two; the figure in brackets is those cases where no information could be obtained except for location details.
The location of the person making the emergency 999 call in relation to the patient is
summarised in table 8.3.3. Only 41.6%, (n =42; 95% CI 32.0-51.8) of callers were close
enough to the patient to allow questioning of the patient, assessment or first aid, following
advice, to be undertaken without leaving the phone. In only two of these cases was the patient
the caller. A further 28 callers (27.7%, 95% CI 19.5 – 37.7) could get to the pa tient but had to
leave the phone to do so. In this group, the caller was a relative in 12 cases, a receptionist in 4
cases and health service related in 5 cases.
Table 8.3.3. Location of person making emergency 999 call
Location No. % 95%CI
a) Present within talking distance of patient 42 41.6% 32.0-51.8
b) Can speak with/assess patient but needs to leave phone to do so
28 27.7% 19.5-37.7
c) Distant from patient, not in contact 5 5.0% 1.8-11.7
d) Only indirect contact possible, for example, via radio
26 25.7% 17.8-35.6
TOTAL 101 100%
123
26 cases (25.7%, 95% CI 17.8-35.6) were in indirect contact with the patient. 10 were police
officers via their control, 4 were fire service, 2 were other ambulance services, 3 were site
security / reception, 3 were local bus services, 2 were deputising services, one was social
services and one was a friend. The identity of the caller is summarised in figure 8.3.1.
3 Hoax calls
24 relatives
4 health workers*
3 friends
2 patient was caller
9 others
42present
13 relatives
4 receptionists*
3 health workers*
2 home carers*
2 friends
4 others
28in vicinity
4 left scene
1 not known
5no contact
10 police*
4 fire*
3 security/reception*
3 bus company*
2 other ambulance*
2 Doctors deputising*
1 social services*
1 friend
26indirect contact
101 cases analysed
104emergencyambulance
calls
Figure 8.3.1. Who calls for the emergency ambulance?
*Indicates those targeted for a call reminder card (see conclusions)
The remaining 5 callers (5%, 95% CI 1.8-11.7) had no means of contacting the patient.
124
8.3.4. Limitations
No attempt has been made to determine the accuracy of the information obtained from the
callers. This study therefore represents the best case scenario presuming All callers gave
accurate information and were able to carry out instructions.
There is no reason why this sample should not be representative of general calls to the
ambulance service studied and the findings should therefore be generalisable. There may be
some differences in the extent of communication problems between ambulance services
according to the ethnic mix and other demographic features of the community served.
Duplicate calls may be underestimated as these invariably occur simultaneously and one
assessor can only monitor one call.
8.3.5. Conclusions
West Midlands Ambulance Service (WMAS) serves a population of 2.3 million people92, in a
mainly urban environment. The majority (84.8%) are white. However, other self-reported
ethnic groups comprise South Asian (9.9%) (including Indian 5.6%, Pakistani 3.6%.and
Bangladeshi 0.7%), Chinese (0.6%), Black (3.9%) and Other (0.8%). This population
therefore has a higher proportion of South Asian people than Great Britain as a whole (2.8%).
Those reporting their ethnic group as white or black generally speak English93,94. Among the
South Asian groups, the ability to speak English varies by group. In those aged 16-74, 85% of
Indians, 72% of Pakistanis and 59% of Bangladeshis speak English94. If these figures are
extrapolated for the population served by WMAS, then 2.3% of the population are not likely
to speak English. Applying these figures to the 0.2 million calls received per year by WMAS,
then non-English speaking people will make 4,200 calls per year. There will be a further
substantial number who do not have English as their first language where communications
may therefore be hampered. This calculation also excludes visitors to the area.
It is surprising, with such a high prevalence of non-English speaking people, that in only one
case did the call taker not manage to obtain medical details and in only three cases did it delay
or restrict the communication. This may be rela ted to the fact that non-English speakers will
usually get access to someone speaking English before making an emergency call. It is not
known whether this causes any delay in accessing the emergency system.
125
It is to be expected that people making emergency calls will be emotional and excitable.
However, a study of cardiac arrests in Vienna had no distraught callers in a series of 59
cases69. In this series, in only 5% of cases did this delay the call taking and in none did it
prevent reception of information. This is mainly due to the call takers being trained in the
management of such situations. The callers may be able to carry out first aid instructions if
calmed down by the call taker. The one abusive caller may reflect alcohol consumption or
anxiety and he would not co-operate with information gathering. The three cases of
misunderstanding were due to specific terms (medication, conscious) in the prioritisation
system and were solved by the use of simpler language.
Although 93% of households have a telephone95, many accidents occur outside the home. If
the caller does not have direct access to the patient, gathering further information and giving
first aid advice is unlikely to be effective. In only 42 cases (41.6%, 95% CI 32.0-51.8), was
the caller close to the patient. Any prioritisation and advice system handling emergency
ambulance calls will therefore have difficulty. Even those callers in the vicinity of the patient
will experience problems as the process is interactive - needing a progression of questions and
serial instructions which may take an excessive time if the caller is shuttling between the
phone and the patient. The two major prioritisation systems gain much of their information on
only four to six questions. At present less than half of emergency ambulance callers are with
the patient. This is similar to the 55% noted in cardiac arrest cases in Vienna69. In Seattle, the
city of origin of CBD, only 29% of cardiac arrests had advice delayed by the caller not being
near the patient96. This is likely to severely restrict accuracy of prioritisation systems in the
UK and the ability to give first aid advice, which often involves many steps. The caller cannot
be expected to comprehend and carry out more than two instructions at a time. Going from
phone to patient or via a third party is likely to be ineffective. Community first aid
programmes and targeting first aid advice on key personnel will continue to be vital when
such a large proportion of 999 callers are not with the patient. Those who only need
reminding of first aid rather than immediate teaching may be able to absorb more complex or
longer instructions and then leave the phone to go to the patient.
To assist prioritisation it may be more effective to issue key organisations with a call reminder
card, listing key information to be obtained before phoning 999 , than attempting to obtain
information indirectly via a third party during the emergency. If such a card were issued to
126
emergency services, travel company controls, health care organisations and home carers
(marked * in figure 8.3.1), it would improve the quality of information in 35 of the cases,
representing 59% of those not with the patient. This advice could also be included in
telephone directories and telephone boxes.
This study demonstrates the inherent difficulties for any prioritisation or advice system
associated with the 999 emergency call system, because of the location of the caller and
associated communication difficulties. It also highlights important differences between the
study area in the UK and Seattle, where CBD originated, and where most of the supportive
research has been undertaken.
A larger study has now been undertaken and has been published97.
127
8.4 CBD usage at a time of exceptional workload
8.4.1. Introduction
If all emergency ambulance calls could receive an immediate response from an ambulance
travelling in emergency mode then there would be no need for prioritisation. There are two
major reasons why this does not occur. Firstly, there are times when the demand for
ambulances outstretches the resources available. Secondly, responding in emergency mode is
hazardous and therefore should not be undertaken unnecessarily for the safety of the
ambulance personnel and the public. The components of this thesis have already raised
concerns over whether CBD is safe and effective at categorising patients according to severity
of illness. Once cases have been prioritised then that prioritisation must be utilised
operationally for CBD to be effective. This element of the study looks at how CBD
prioritisation categories are utilised at times when resources are limited compared to the
demand.
New Years Eve is a catalyst for large mass gatherings with the potential for high numbers of
casualties. It is said to be the busiest period of the year for the ambulance service. In 1997/98
in Edinburgh, a 50% increase in A&E department staffing was insufficient to resolve the
problems of increased attendance 98. The New Year of 1997/98 was the first New Year when
999 call prioritisation was operational in the UK. Periods of maximum workload are the
ultimate test of this resource allocation system. Category “A” calls should receive a faster
response than Category “B” or "C". However, no previous research has looked at whether
prioritisation achieves its purpose as a tool for managing excessive workload.
The West Midlands Ambulance Service (WMAS) database holds records for every 999
emergency ambulance call received by the control room. Each incoming call is automatically
assigned an individual identity number by the control system software. Duplicate calls for the
same incident are cross-referenced manually and the records of the ambulance respons e stored
with the first call logged. The log also contains details of all the units that were responded to
the incident and their time of arrival at scene. The latter time is recorded via the satellite
128
tracking system on depression of a button in the ambulance cab. All calls are logged to the
nearest second.
8.4.2. Aim of this study
The aim of this study was to determine whether the ambulance prioritisation system allows
the most urgent cases to receive a priority response at a period when demand massively
exceeds the resources available.
8.4.3. Methods
Data on all incidents occurring in the first eight hours of 1998 (1st January 00.00 hrs. to 07.59
hrs.) were downloaded from the WMAS control database. The number of calls per hour was
compared with the hourly average for the same time period in the first seven days of
December 1998. The response time (from the ambulance service telephone answering to the
arrival of the first ambulance service response) for each incident was assessed according to
the time of day and the prioritisation system category. Adequate data were defined as those
incidents with times recorded, to allow calculation of response times, and where the
prioritisation system category was recorded.
Analysis was undertaken to determine whether response times varied according to the
prioritisation system category. Mean response times were calculated for the eight-hour period,
with standard deviations. To allow for isolated exceptionally long response times, the number
of incidents responded to within ORCON42 time frames for urban ambulances were
calculated. Category “A” calls have an ORCON target time of 8 minutes and Category “B”
and “C” calls of 14 minutes. Thirty and sixty minute response times are also included for
completeness. These response times were also calculated for each one -hour period of the
eight-hour study period.
8.4.4. Results
A total of 494 999 calls were received in the eight hour study period, relating to 380 incidents
(average 1. 3 calls per incident). This represents an average call reception rate of over one per
minute (62 per hour), ranging from 6 calls per hour between 06.00 hrs. and 06.59 hrs. to 88
calls per hour between 01.00 hrs. and 01.59 hrs. (figure 8.4.1.). The number of calls was
129
substantially greater than the workload for this time period in the comparator week, which
averages 16.4 calls per hour with a peak hourly rate of 30.4.
0102030405060708090
100
00:0 01:0 02:0 03:0 04:0 05:0 06:0 07:0Tim
Cal
ls p
er h
our
New Years Comparator
Figure 8.4.1. Hourly 999 call rate compared to a control time period.
Inadequate data were recorded for 126 incidents (all with incomplete time recording, one with
no priority code). There was no difference in the distribution of the prioritisation categories
between cases with adequate and inadequate data. Adequate data were available for 254 of the
380 incidents and these were included in the following analyses. Of the incidents with
adequate data, 69 (27.2%) were Category "A", 136 (53.5%) were Category “B” and 49
(19.3%) were Category "C". In the one week control period, for patients presenting between
00.00 hrs. and 07.59 hrs., Category “A” patients accounted for 28.6%, Category “B” for
59.2% and Category “C” for 12.1% (see table 8.4.1). There is no significant difference in the
proportions of Category “A” and “B” patients between the New Year and a control group
matched for time of day.
130
Table 8.4.1. Emergency ambulance calls by prioritisation category for New Year’s Eve and a
control period.
New Year Control
A 69 (27.2%) 85 (28.6%) p = NS
B 135 (53.5%) 176 (59.2%) p = NS
C 49 (19.3%) 36 (12.1%) p<0.05
n = 253 297
The percentage of incidents responded to within 8 minutes in category “A” and within 14
minutes for categories “B” & “C”, with variation by time of day is shown in table 8.4.3. No
significant difference was observed in the proportion of Category “A” cases achieving the
eight minute response (the new standard for Category “A” patients) compared to those in
Category "B". The same is true for the 14 minute response.
Table 8.4.2. Percentage of ca lls responded within 8 and 14 minutes.
Time (GMT)
Response time
(mins)
00.00 01.00 02.00 03.00 04.00 05.00 06.00 07.00 All CBD
cat-
egories
0 - 8 38.9% 21.4% 7.7% 16.7% 20.0% 50.0% 0.0% 75.0% 29.0% A
0 - 8 42.9% 25.0% 15.4% 26.9% 38.9% 52.9% 57.1% 30.8% 33.5% B&C
p = NS NS NS NS NS NS NS NS NS
0 - 14 72.2% 64.3% 46.2% 33.3% 80.0% 87.5% 100.0% 100.0% 66.7% A
0 - 14 76.2% 52.8% 38.5% 73.1% 88.9% 82.4% 100.0% 84.6% 69.2% B&C
p = NS NS NS NS NS NS NS NS NS
>14 27.8% 35.7% 53.8% 66.7% 20.0% 12.5% 0.0% 0.0% 33.3% A
>14 23.8% 47.2% 61.5% 26.9% 11.1% 17.6% 0.0% 15.4% 30.8% B&C
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Average response times and the range of response times by category are shown in table 8.4.3.
Table 8.4.3. Average response times and the range of response times by category.
CBD category mean SD max. min incidents with adequate data
Category A 13 9.6 53 4 69
Category B 14 12.0 66 0 135
Category C 14 10.8 55 0 49
All cases 14 11.2 66 0 253
Exceptional delays (>30 minutes) were experienced in 19 cases. Of these 5 (26%) were
Category “A” calls, 3 occurring between 02.29 hrs. and 02.43 hrs. Thirteen (68%) of the
delays occurred between 01.31 hrs. and 02.31 hrs. In this one hour period only 2 of 15
(13.3%) Category “A” calls were responded to within the target 8 minutes and only 14 of 30
(46.7%) “B” calls within the target of 14 minutes. Two cases (both category "B") waited over
an hour.
8.4.5. Limitations
This study only looks at the experience of one ambulance service in one year. One third of
incidents have missing data, which probably reflects the excess of demand over resources
within the control room. However, the distribution of the prioritisation system codes in the
adequate data sample and in the whole population is not significantly different.
The observed results could relate to the use of the prioritisation system by the particular
ambulance service studied or the particular people working the shift concerned. However, the
conclusions do reflect the prioritisation system in actual use. There is no reason to believe the
results should not be representative of ambulance service practice in the UK.
8.4.6. Discussion
This study confirms that New Year's Eve is an exceptionally busy period for ambulance
services with high hourly call rates. From midnight until 06.00 hrs. demand is markedly
increased on this night of the year. The number of calls reaches a peak between 01.00 hrs. and
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01.59 hrs., with a four -fold increase in 999 call volume over normal for three consecutive
hours. The outcome study showed that West Midlands Ambulance Service achieves national
targets, however these are not achieved on New Years Eve. During this period response times
are markedly delayed, with occasional waits of over an hour occurring for a 999 ambulance.
New Year’s Eve does not have any special requirements because of any increased severity of
illness as predicted by CBD. The popular belief among ambulance services that more low
priority cases are seen in this time period is supported by this study, although the proportion
of Category “A” cases is no different.
To ensure that a rapid response is maintained to those whose condition may deteriorate if
ambulance arrival is delayed, prioritisation systems should be used when demand exceeds
resources. It is worrying to obs erve that response times do not appear to vary according to the
prioritisation system category. No variation in response times is demonstrated in either
absolute numbers of calls or the percentage of that category (both of which should reflect the
prioritisation effect). In all but the final one hour time period, the percentage of cases
achieving an eight-minute responses was better in categories “B” & “C” than in category A,
although the observed differences were not statistically significant. No difference was seen in
the fourteen-minute response between prioritisation categories. It appears therefore that either
the prioritisation system was not being used to give a more urgent response to those classified
as Category “A”, or the available resources were insufficient even to cope with responding to
the Category “A” cases. Failure to use the system may result from staff changing to the more
familiar, traditional and simpler, but not necessarily safer, method of “first come, first served”
allocation of resources. At times when the ambulance service is exceptionally busy, one
would expect the prioritisation system to be utilised as a risk management tool.
8.4.7. Conclusions
The figures presented suggest that the ambulance service may need to increase its resources
on New Year’s Eve between midnight and 04.00 hrs. to be able to maintain normal response
standards. Alternatively, ambulance services need to look at other ways of managing this
exceptional workload. This may include use of first responders or doctors to assess the need
for an ambulance, use of the voluntary aid societies or use of a non-ambulance response (for
example, taxi) for non-urgent cases. An alternative approach may be to decrease turnaround
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time for ambulance availability by delivering appropriate patients to other local facilities, such
as primary health care centres with provision for minor injury care.
Category “C” patients accounted for 19% of cases and will include those who may not need
an ambulance immediately. A non-ambulance response may be appropriate for such cases and
this is discussed in the conclusions of this thesis.
If the prioritisation system is not being utilised at times of maximum workload, then its use
overall is put into question. The time required for dispatchers to ask the extra questions and
the cost of the extra training are wasted if no advantage results. It may be better to spend the
money that would be invested in prioritisation systems in refining deployment strategy or
training and staffing more response units. Alternatively, ambulance services need to assess
why the prioritisation system is not being utilised and address those problems. At present the
prioritisation system appears to represent a large investment that is failing to deliver benefits
in resource utilisation during periods of high demand.
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9. Conclusions
The existing literature that is applicable to the UK in regard to prioritisation of ambulance
calls is sparse. What exists has highlighted some of the advantages of prioritising 999 calls by
an earlier response and the ability to respond more highly trained crews. In the UK, there is a
paramedic in every ambulance and so the latter advantage is not applicable. The literature has
also demonstrated that more efficient operational use of ambulance is possible with
prioritisation. However, clinical benefits have been only variably demonstrated. Failure to
detect serious cases has been recorded in some specific patient groups but has never been
closely analysed.
The outcome and ambulance alerts studie s in this thesis have demonstrated that the use of
CBD does have some significant safety issues. It must, however, be remembered that prior to
the introduction of call prioritisation all ambulance calls were responded to equally with a
target time of 14 minutes. Failure of the system to detect serious cases does not therefore
confer any disadvantage over the previous system; it simply fails to instigate the improvement
of care that was a cornerstone of the argument for the introduction of CBD. The effects of this
delay are generally unknown. The time to first medical assistance has been shown to be
important in varying scenarios17, 18, 19.
The degree to which CBD fails to detect all the potential time dependant critical illnesses has
not been extensively described and is a major finding of this thesis. This failure of the system
can be measured in many ways. The opinion of experts in the outcome study suggested that
the system failure rate was 16.7% - 38.4% overall. This study has also hypothesised that the
dispatchers use the system for guidance rather than as a strict rule book; in this way they
improve the system and reduce the under-triage rate of the system. The broad range partly
reflects the problems with using expert opinion. There are specific cases where urgent care
was required to prevent further deterioration. In these cases where either the ambulance crew
or the receiving team in the accident and emergency department commenced urgent treatment,
there was a failure to detect the seriousness of the problem by the dispatching system in up to
69% of cases. The other scenario when emergency care can be presumed to be needed is when
there is gross physiological abnormality such as airway obstruction, respiratory distress or
unconsciousness. In these situations, in up to 55% of occasions the problem was not detected.
135
In cases where the ambulance crew thought the patient was ill enough to require a team
standing by at the hospital, the dispatcher using CBD did not detect at least 20% of cases. The
error rate appears highest in the most seriously ill, the group which prioritisation is meant to
benefit.
It appears from various aspects of the work in this thesis that an over-triage rate of 50% will
occur because of the safety margin required. Attempts to reduce the over-triage rate below
this should be undertaken cautiously with full evaluation. It is unlikely that information from
a 999 call will ever improve on an expert’s opinion with information from the patient after
arrival in hospital, which over-triaged half of cases.
Often the predicted need for emergency intervention was not substantiated when the eventual
diagnosis was known. This final diagnosis may only be known after hospital investigation,
such as after an x-ray to exclude a neck injury. Nevertheless even when looking with the aid
of all diagnostic tests to make the diagnosis, at least 10% of patients who needed a category
“A” response were not triaged as such.
Criteria Based Dispatch cannot therefore be currently stated to be effective at detecting life
threatening illness and injury.
Expert opinion of the CBD system studied in this thesis has shown that there are many areas
of concern. In only 16.4% of codes did a majority of all expert groups agree with the
prioritisation. In 46.6% the majority disagreed. When asked to give their opinion of the
prioritisation with previous knowledge of the codes, a group of experts gave different priority
to 39% of codes. These have been backed up by the other elements of this study. This
summary of the conclusions focuses on those issues, which were detected by multiple
elements of the study. Individual issues have already been mentioned in the chapter
conclusions. It is recommended that a review should be undertaken of all these areas of
concern in developing a safer and more effective system of prioritising 999 calls.
Uncontrolled haemorrhage was detected as a major cause of under-triage. Whatever the
source of bleeding, if it cannot be controlled then serious consequences will occur. The
ambulance services first action to stop this bleeding should be by giving first aid advice.
However, the communication difficulties study demonstrated that less than half of callers are
136
within talking distance of the injured party. Hence telephone first aid advice will often not
resolve the problem. It is therefore appropriate to respond a person sufficiently skilled to stop
the haemorrhage at the earliest time. Hence, all situations with uncontrolled haemorrhage
should have a category “A” response.
Any person with a decreased level of consciousness is at risk. Their airway may be
compromised because of their inability to control their own airway. Equally they are unable to
protect their own airway, so saliva, vomit or blood may obstruct the airway. This will lead to
death or severe neurological injury within minutes. Hence a response within 8 minutes is
vital. CBD gives a category “A” response for people who are unconscious but not those with
a decreased conscious level. It is known that the public does not understand the term
unconscious80, let alone the detail of difference between unconscious and decreased conscious
level. Any decrease in conscious level is a risk to the patient and also a sign of potential
serious impairment or illness. I recommend that all people with any lowering of conscious
level should be categorised as "A". This could be achieved by asking whether the person can
talk. Other errors resulted from the discrepancy between CBD and nationally accepted
guidelines for head injury management85.
Errors were detected in the outcome and alerts studies because of persons reported to be
fitting. Fitting is most commonly due to eplileptiform seizures. However, there can be many
other causes. Lack of oxygen to the brain because of airway obstruction, inadequate
ventilation or poor tissue perfusion can all cause fits. Usually, the fits of brain hypoxia are
short lived, followed by unconsciousness and then death, if no corrective action is undertaken.
The majority of these problems could be solved by introducing a new code of “fits continuing
or not talking since fit” and by limiting the use of “fit, unknown cause” to have the additional
statement of “now recovered”.
The threat to life posed by burns injuries can be difficult to assess. It is well recognised that
people with severe burns can initially be walking and talking but die soon after. Burns to the
airway can be difficult to detect and can deteriorate very rapidly. All burns to the face or
sustained in a closed environment, with the risk of smoke or hot air inhalation, should
therefore be categorised as “A”. The criteria for severe burns by surface area is 15%. This is
the nationally accepted level at which resuscitation should be commenced in adults. The body
surface area in children for resuscitation is 10%. There is no information to suggest how well
137
this can be estimated on the telephone, so any burn of a whole limb, the front of the chest or
equivalent area should be presumed to be over the limit and categorised as “A”. Burns due to
electrocution have the risk of cardiac arrhythmias and those due to chemicals need rapid
decontamination and so should receive an urgent response.
Diabetics represent a special group of patients. In particular, the onset of hypoglycaemia can
be highly variable in duration and appearance. Hypoglycaemic episodes were missed because
the diabetic was classified as being “unwell” and then deteriorated further. Any fainting,
unusual behaviour, sweating or short duration of being unwell should be presumed to be due
to hypoglycaemia. At present none of these receive a category “A” response. The other
common metabolic emergency is related to overdoses. Certain overdoses can initially appear
well and then suddenly deteriorate often due the drug’s cardiotoxic effect. CBD would not
detect such high-risk overdoses. A question asking about the type of medication taken should
help to resolve this issue.
The elderly often have atypical presentations of common conditions. Falls are often due to an
underlying medical cause, such as palpitations or vertigo. Faints can be for more serious
reasons than simple vasovagal episodes. Hence the codes for "falls no injury" and "simple
faint" should be limited to the younger age group and those in whom it is certain there was no
predisposing cause. Children under two years of age are all classified as category "A".
Experts thought this could be downgraded in some cases. Because of the difficulty in
assessing this age group and the speed with which they can deteriorate, combined with the
small numbers involved, it may be better to leave this group uncha nged.
Road accidents often have multiple telephone calls and many are reported on mobile phones
by people who have passed the incident and have not stopped to see the victim. Hence there is
often insufficient information to determine the victim's clinical condition. ATLS gives
guidelines for mechanisms of injury that are high risk and these should be all categorised as
"A". Falls were also noted in both the alerts and outcome studies to have been under -triaged.
Similarly falls greater than 10 feet for adults are known to be high risk and should be
reclassified.
Lack of information occurs in 15% of calls because of communication difficulties and when
the caller away from the victim this problem is increased. If there is insufficient information,
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then a higher prioritisation code should be used. In CBD there are several instances where the
unknown history is classified as category "C". In the interests of safety this should be
changed.
Many of the changes recommended above are consequent on changes made to the American
system when it was introduced into the UK. The problems relate to decreased conscious level,
haemorrhage and road traffic accidents would not have occurred if the American system had
been used without change.
CBD needs to be reviewed to ensure that the cases highlighted above will receive a category
“A” response in the future.
Another proposed use of CBD is in detecting those patients who may not need a 999
ambulance response. It has been suggested that category “C” calls could be dealt with in this
way. However, this study has highlighted that category “C” does not equate exclusively with
minor illness or injury. The examples cited above demonstrate that many of the present
category “C” calls may need a category “A” response. This may be par tially solved by a
recoding. The system proposed by Dale and others89 of passing category “C” calls over to
NHS Direct who can then undertake further interrogation to determine the most appropriate
and safest response. In his study, Dale demonstrated that half of category “C” calls did not
require an emergency ambulance. The survey of those not transported, in this thesis, has
shown that there is a high proportion of patients currently calling 999 who could be using
other services, if a method of detecting which service could be developed and the resources
were made available. This system cannot, however, be used as a safety net for poor initial
prioritisation, as it does inevitably result in a delay of the ambulance response because of the
further interrogation.
If prioritisation is to be effective then action must be taken appropriate to the category
ascribed to cases. This study has shown that there is no significant difference in ambulance
response times according to CBD category. Even at a time of high workload when the
ambulance service were overloaded with cases (New Year’s Eve), the prioritisation category
was not a determinant of the speed of response. It appears that the advantages of call
prioritisation for resource usage and patient benefit are being lost.
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This thesis has demonstrated some major weaknesses in one system of call prioritisation
currently used in the UK. No inference can be made as to how the other system performs. At
present the system has a high failure rate in detecting the seriously ill and much of this is due
to system design. There is a need for further work to examine how critically ill and injured
patients can be more accurately detected from a 999 call. Until this work has been done
people should not presume that 999 call prioritisation codes equate to severity of illness. At
present CBD is simply a guide to the possible severity of a persons condition.
Although CBD is only currently used by some ambulance services for prioritisation of 999
calls, the use of prioritisation of emergency workload is increasing. The National Health
Service is developing a system of clinical assessment that can be used either by telephone or
face-to face. The development of such systems has an initial assessment to exclude serious
illness or injury. As this is developed the principles and problems highlighted in this thesis
should be taken in to account so that similar problems are not re-invented.
Summary
The initial expert opinion highlighted a cause for concern due to the poor level of agreement
with the CBD system. The literature review demonstrated that the system was not founded on
a strong evidence base and that there had been no rigorous evaluation of the system. The
outcome study has demonstrated an under-triage rate of 12.6% - 25.6%, when comparing
actual dispatch prioritisation with expert opinion with knowledge of eventual diagnosis. The
actual system has a higher rate that is corrected by the intervention of the dispatcher. The
patient’s early or late outcome does not seem to relate accurately to their CBD coding. The
outcome study also highlighted that certain seriously ill patients, especially diabetics, those
having fits, those suffering trauma, those with airway obstruction, potential spinal injury and
who are unconscious may be at particular risk. The alerts study has demonstrated that at least
20% of critically ill patients may not be detected by CBD. The particular areas of concern are
the failure to recognise cardiac arrests; the miscodings are often related to fits, severe
bleeding, unconsciousness, falls/faints and the use of mechanism of injury rather than clinical
state. Many of the areas of concern that have been determined in the outcome study and the
alerts study could potentially have been prevented by not changing the American system of
CBD when it was adopted in the UK.
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The outcome study has demonstrated that patients initially categorised as “C” are often in
need of monitoring in the ambulance or require a prehospital intervention, although they are
rarely physiologically disturbed. 10% of all admissions and 9% of deaths are categorised “C”.
It is therefore already apparent that it not safe to automatically state that those category “C”
patients are safe to be transferred directly to another source of care. The “non-transport” study
has revealed that many cases that do not need ambulance care are classified other than
category “C”. Category “C” is therefore neither sensitive nor specific for detecting those with
minor conditions that do not require an emergency ambulance response.
Having shown the problems related to prioritisation of emergency ambulance calls using
CBD, the “New Year's Eve” study then demonstrates that the ambulance control centre did
not utilise the prioritisation information in determining how to allocate resources.
It appears that CBD has major flaws. This research recommends that the American system of
categorisation of CBD should be adopted and that specific presenting groups should be
reviewed. The use of category "C" to decide whether to send an ambulance, without any
further prior assessment, does not appear to be safe at present.
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Papers published in relation to this thesis
PEER REVIEWED PUBLICATIONS
Cooke MW, Wilson S. Are 999 callers in a position to give triage information and receive first aid advice. Pre –Hospital Immediate Care 1998;2:193-196. Cooke MW, Morrell R, Wilson S, Allan T, Bridge P, Edwards S. Does Criteria Based Dispatch adequately detect the critically ill and injured? Prehospital Immediate Care 1998;2:52. Wilson S, Edwards S, and Cooke MW. Inappropriate ambulance usage is a retrospective diagnosis. Journal of Accident and Emergency Medicine 1999;16:75. Cooke MW and Jinks S. Planning cannot rely on emergencies arriving by ambulance. Journal of Accident and Emergency Medicine 1999;16:74-75. Cooke MW, Wilson S, Allan T and Bridge P. Will prioritisation of 999 calls help ambulance services cope with the Millennium celebrations? Prehospital Immediate Care 1999;3(4):203-205. OFFICIAL REPORTS
Cooke MW, Wilson S, Allan T, Bridge P, Edwards S, Morrell R. Safety and effectiveness of criteria based dispatch in the prioritisation of 999 calls. Emergency Medicine Research Group, University of Medicine, Birmingham 1998. OTHER PUBLICATIONS – not peer reviewed
Cooke MW, Wilson S, Allan T, Bridge P, Edwards S, Morrell R. Safety and effectiveness of criteria based dispatch in the prioritisation of 999 calls. What Matters: Research and Development News – West Midlands Region. 1998 Issue 8, p4. INVITED LECTURED AND SEMINARS
Cooke MW. Measuring Outcome in Dispatch (invited presentation). Ambulance Service Association, London 24 September 1998. Plenary. CONFERENCE PROCEEDINGS & OTHER PRESENTATIONS Cooke MW, Morrell R, Wilson S, Allan T, Bridge P, Edwards S. Does Criteria Based Dispatch adequately detect the critically ill and injured? (oral presentation) Conference of Pre-hospital Immediate Care, London (5 March 1998). Parallel session.
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Cooke MW, Wilson S, Allan T, Bridge P, et al. Is CBD applicable on an international basis? (Emergency Care Conference, Johannesburg, South Africa 5-10 October 1998) Parallel session. Harrison JF Cooke MW, Early Warning of Accident and Emergency Departments by Ambulance Services. (oral presentation) Conference of British Association for Accident and Emergency Medicine, Birmingham 29 April-1 May 1998 (Abstract in Journal of Accident and Emergency Medicine 1998;15:278).
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Appendix One The CBD (UK)coding system Chief complaint Condition Code Abdominal / Back P ain Unconscious or not breathing 1A1
Difficulty in breathing 12 to 50 years with fainting / dizziness
1A2
Lower abdominal pain, female 12 to 50 years with fainting / dizziness
1B1
Vomiting red blood 1B2
Black tarry stools 1B3
Upper abdominal pain , more than 35 years 1B4
Abdominal / back pain, more than 50 years with fainting / dizziness
1B5
Fainting / dizziness when sitting up 1B6
Side / back pain 1B7
Pain with vomiting 1B8
Unspecified pain 1C1
Abdominal / back pain less than 50 years (Non Traumatic)
1C2
Chronic back pain 1C3
Allergic Reaction Unconscious or not breathing 2A1
Difficulty breathing or swallowing 2A2
Cannot talk in full sentences 2A3 Swelling in throat 2A4
Fainting 2A5
History of severe reaction occurring less than 30 minutes of exposure
2A6
History of severe reaction but none now 2B1
Call delayed more than 30 minutes with history of reaction
2B2
Reaction to medication 2B3
Itching and / or rash with no difficulty breathing 2C1 Concern about reaction but no history 2C2
Reaction present for some time with no difficulty breathing
2C3
144
Appendix One (contd.)
Animal Bites Unconscious or not breathing 3A1
Difficulty in breathing 3A2
Uncontrolled bleeding 3B1 Severe bites to face and/or neck 3B2
Bite from poisonous animal 3B3
Bite below neck with controlled bleeding 3B4
Minor bite below neck non-poisonous 3C1 Swelling at bite site 3C2
Bleeding (Non Trauma) Unconscious or not breathing 4A1
Multiple fainting episodes 4B1
Fainting or near fainting when sitting 4B2
Vomiting blood (red / dark red) 4B3
Coughing up blood (red / dark red) more than 1/2 cup
4B4
Lower abdominal pain female 12 to 50 years with associated heavy vaginal bleeding
4B5
Sweating 4B6
Black tarry stools 4B7
Vaginal bleeding more than 20 weeks pregnant 4B8
Bleeding without 'A' criteria 4B9
Vomiting up coffee ground like substances 4B10
Weakness 4B11 Uncontrolled nose bleed 4B12
Vaginal bleeding without fainting less than 20 weeks pregnant
4B13
Rectal bleeding without "B" criteria 4C1
Vaginal spotting 4C2
Nose bleed without "A" or "B" criteria 4C3
145
Appendix One (contd.)
B reathing Difficulty Unconscious or not breathing 5A1
Inhaled Substances 5A2
Unable to talk in full sentences 5A3
Difficulty breathing with chest pains 5A4
Children less than 12 years with history of asthma or respiratory problems
5A5
Difficulty breathing more than 50 years 5B1
Recent childbirth / broken leg / hospitalisation within last 2-3 months
5B2
Drooling / difficulty swallowing 5B3
Asthma unresponsive to medication 5B4
Less than 50 years without 'A' criteria 5B5
Tingling or numbness in extremities or around mouth
5C1
Blocked up nose and / or cold symptoms 5C2
Patient assistance 5C3
Cardiac Arrest Unconscious or not breathing 6A1
Suspected sudden death 6A2
Sudden infant death syndrome 6A3 Very obviously dead / burned beyond recognition
/ rigor mortis present 6C1
Chest Pain Unconscious or not breathing 7A1
Short of breath cannot talk 7A2 Fainting 7A3 Severe chest pains with sweating 7A4 Rapid heart rate with chest pains or medical
history of heart problems 7A5
Male more than 35 years 7B1 Female more than 40 years 7B2 15 to 35 years with shortness of breath / nausea /
sweating 7B3
With drug abuse 7B4 Male less than 35 years without 'A' or 'B' criteria 7C1 Female less than 40 years without 'A' or 'B' criteria 7C2 Rapid heart beat without 'A' or 'B' criteria 7C3 Chest injury less than 35 years without 'A' or 'B'
criteria 7C4
146
Appendix One (contd.)
Choking Unconscious or not breathing 8A1
Unable to talk or cry 8A2
Turning blue 8A3
Difficulty / noisy breathing 8A4
Able to speak or cry 8B1
No difficulty breathing at time of call 8B2
Diabetic Unconscious or not breathing 9A1
Severe difficulty breathing 9A2
Fitting 9A3
Decreased level of consciousness 9B1
Fainting 9B2 Chest pain 9B3
Unusual behaviour / acting strange 9B4
Sweating 9B5
Awake / alert 9C1 Not feeling well 9C2
Weakness 9C3
Environmental Unconscious or not breathing 10A1 Severe difficulty breathing 10A2
Confused / disorientated 10B1 Fainting 10B2
Chemical on patient without other criteria 10B3
Uncontrollable shivering 10B4
Excessively hot 10B5
Minor injuries without 'A' or 'B' criteria 10C1
No injuries but patient has been exposed 10C2
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Appendix One (contd.)
Fits / Convulsions Not breathing after fit stops 11A1
Continuous fits more than 5 mins 11A2
Multiple fits 11A3
Pregnant 11A4
Secondary to recent head injury 11A5
Diabetic 11B1
Secondary to drug overdose 11B2
Fit unknown history 11B3
Fit / convulsion less than 6 years 11B4
Single fit, known history of fitting disorder 11B5
First time fit more than 6 years 11B6
Gynaecological / Miscarriage
Unconscious or not breathing 12A1
Vaginal bleeding with fainting 12A2 Fainting or near fainting when sitting up 12A3
Abdominal injury with contractions more than 24 weeks pregnant
12A4
Lower abdominal pain 12 to 50 years if associated with dizziness / fainting or heavy vaginal bleeding
12A5
Sweating 12B1
Bleeding more than 20 weeks pregnant 12B2
Vaginal bleeding without fainting 12B3
Abdominal injury without contractions more than 24 weeks pregnant
12B4
Waters broken 12B5 Pregnant less than 20 weeks or menstrual with any
of the following: cramps pelvic pain
spotting
12C1
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Appendix One (contd.)
Headache Unconscious or not breathing 13A1
Decreased level of consciousness 13B1
Mental confusion 13B2
Worst headache ever 13B3
Sudden onset 13B4
Physical exertion 13B5
Head injury without 'A' criteria 13B6
Headache without 'A' or 'B' criteria 13C1
Migraines 13C2
Mental/Emotional Unconscious or not breathing 14A1
Gunshot wound / stab to head, neck, torso or thigh 14A2 Unusual behaviour associated with diabetes 14B1
Suicidal overdose of medication 14B2
Lacerated wrist 14B3
Unusual behaviour associated with psychiatric history
14B4
Unusual behaviour due to drugs 14B5
Known alcohol intoxication 14B6
Threats to self or others 14B7
Police request standby 14C1
Overdose / Poisoning Unconscious or not breathing 15A1
Severe difficulty in breathing (unable to speak in full sentences)
15A2
Difficulty in swallowing 15B1
Decreased level of consciousness 15B2 Intentional / accidental drug overdose 15B3
Ingestion of household cleaners 15B4
Acute alcohol intoxication less than 17 years 15B5
Alcohol or drug overdose 15B6
Drug overdose with chest pain 15B7
Third party caller not with patient 15B8
Chemicals ingested / splashed on skin 15B9 Drug use without “A” or “B” criteria 15C1
Alcohol intoxication without drugs more than 17 years
15C2
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Appendix One (contd.)
Pregnancy / Childbirth Unconscious or not breathing 16A1
Vaginal bleeding with fainting 16A2
Fainting or near fainting when sitting up 16A3
Fitting 16A4
Delivery 16B1
Labour pains / contractions:
less than 2 mins 1st pregnancy less than 5 mins 2nd pregnancy
16B2
Bleeding more than 20 weeks pregnant 16B3
Premature labour more than 4 weeks 16B4
Abdominal injury more than 24 weeks 16B5 Vaginal bleeding without fainting 16B6
Waters broken 16B7
Labour pains:
more than 2 mins 1st pregnancy more than 5 mins 2nd pregnancy
16C1
Pregnant less than 20 weeks with abdominal pain / spotting
16C2
Sick / Unknown Unconscious or not breathing 17A1
Multiple fainting episodes 17B1 Decreased level of consciousness 17B2
Chest discomfort more than 35 years 17B3
Indigestion more than 35 years 17B4
Dizziness when standing 17B5
Generalised weakness 17B6
Third party caller not with patient 17B7
Medical alarm from Social Services 17B8
Other problems without other criteria 17B9
Flu symptoms 17C1
High blood pressure 17C2
High temperature 17C3 Patient assistance 17C4
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Appendix One (contd.)
Stroke / CVA Unconscious or not breathing 18A1
Severe difficulty breathing 18A2
Fitting 18A3
Decreased level of consciousness 18B1
Chest pains 18B2
Diabetic 18B3
Severe headache 18B4
One sided hemiplegia 18B5
Weakness, numbness 18B6
Trouble speaking 18B7
Unconscious Unconscious or not breathing 19A1 Confirmed unconscious/unresponsive 19A2
Combined drugs and alcohol overdose 19A3
Difficulty breathing 19A4
Alcohol intoxication less than 17 years 19A5 Unconfirmed slumped over wheel 19A6
Third party caller not with patient 19A7
Multiple fainting episodes 19B1
Fainting associated with headache, chest pain / discomfort / palpitation more than 35 years / diabetic / GI bleed.
Vaginal bleed sitting or standing / abdominal pain female 12 to 50 years
19B2
Single faint 19B3
Unconscious but now conscious 19B4
Conscious with minor injuries 19B5
Alcohol intoxication more than 17 years 19B6
Obviously dead - decapitated / burned beyond recognition / cold & stiff, unless child less than 1 year
19C1
151
Appendix One (contd.)
Miscellaneous Airport alert 20A1
Bomb device detonated 20A2
Major incident 20A3
Fire persons reported 20A4
Explosion 20A5
Smoke detector no speech contact 20B1
Firearms incident 20B2
Prison incident 20B3
Chemical incident - stand by 20B4
Riot incident 20B5
Bomb device unexploded 20B6
Fire Service - standby 20B7
Automatic fire alarm 20C1
Police - standby 20C2
Hoax call 20C3
Hoax call children 20C4
Caller cleared unable to call back 20C5
Major incident exercise 20C6
Sporting event 20C7
152
Appendix One (contd.)
Assault / Trauma Unconscious or not breathing 21A1
Crushing or penetrating injury to head, neck, chest, abdomen or thigh
21A2
Decreased level of consciousness 21B1
Uncontrolled bleeding 21B2
Penetrating injury to extremities below shoulder or below knee
21B3
Unknown injury 21B4
Minor injuries with weapons 21B5
Extremity/femur fracture 21B6
Sexual assault/rape without 'A' criteria 21B7
Minor injuries without weapons 21C1
Concerned without apparent injuries 21C2
Police request standby or check patient 21C3
Burns Unconscious or not breathing 22A1
Difficulty breathing 22A2
Difficulty talking / swallowing 22A3
Decreased level of consciousness 22B1
Burns to airway, nose, mouth 22B2
Electrocution / electrical burns 22B3 Burns / scalds more than 15% of body surface 22B4
Battery explosion 22B5
Chemical burns to eyes 22B6
Small burns from match or cigarette 22C1
Freezer burns 22C2
Drowning Unconscious or not breathing 23A1 Difficulty breathing 23A2
Confirmed submerged more than 1 minute 23B1
Scuba diving accident without 'A' criteria 23B2
Patient not submerged 23B3
Patient coughing 23B4
Other injuries without 'A' criteria 23B5 Minor injuries (lacerations) 23C1
153
Appendix One (contd.)
Falls / Accidents Unconscious or not breathing 24A1
Severe difficulty breathing 24A2
Accident with crushing or penetrating injury to head, neck, torso, or thigh or patient trapped
24A3
Decreased level of consciousness 24B1
Amputation above fingers or toes 24B2
Patient paralysed 24B3
Uncontrolled bleeding 24B4 Fall more then 10 feet 24B5
Fall associated with chest pain, dizziness, headache or diabetes
24B6
Was unconscious but now conscious 24B7
Amputation / entrapment of fingers / toes with controlled bleeding
24B8
Multiple extremity fracture or single femur fracture
24B9
Third party caller not with patient 24B10
Cuts, bumps and bruises 24C1
Patient assist / assessment 24C2
Involved in accident no apparent injuries 24C3
Isolated extremity fracture 24C4
Neck or back pain 24C5
Neurological / Head Injury Unconscious or not breathing 25A1
Severe breathing difficulties 25A2
Fit following a head inju ry 25A3 Decreased level of consciousness 25B1
Fall more than 10 feet 25B2
Aggressive behaviour 25B3
Now awake - has been unconscious 25B4
Confused as to what happened 25B5
Bump or laceration from fall without loss of consciousness
25C1
154
Appendix One (contd.)
Road Traffic Accident Unconscious or not breathing 26A1
Difficulty in breathing 26A2
Penetrating injury to head, neck, chest, abdomen or thigh
26A3
Decreased level of consciousness 26B1
Confirmed or unknown injuries with the following mechanism:-
Vehicle vs. immovable object 26B2
Vehicle vs. vehicle (head side on) 26B3
Vehicle vs. pedestrian 26B4
Vehicle vs. motorcycle / bicycle 26B5
Victims trapped / ejected 26B6
Multiple vehicle / casualty incident 26B7
Chest pain prior to accident 26B8
Injury accident without "A" criteria 26B9
Roll over 26B10
Third party caller not with patient 26B11
Minor injuries patient up / out / walking 26C1
Patient assessment required by police 26C2
155
Appendix One (contd.)
Child under 2 years Cardiac arrest 27A1
Unconscious or not breathing 27A2
Breathing difficulty 27A3
Croup / Asthma / Epiglottitis 27A4
Choking 27A5
Fits / Convulsions 27A6
Bleeding - Non Trauma 27A7
Bleeding - Trauma 27A8
Assault 27A9
Head injury / Neurological 27A10
Falls / Accidents 27A11
RTA related injuries 27A12
Animal bite 27A13
Burn 27A14
Overdose / poisoning 27A15
Drowning 27A16
Environmental emergency 27A17
Sick / unknown / other 27A18
Headache 27A19
Mental / emotional 27A20
Chest pains 27A21
Stroke / CVA 27A22
Abdominal / back pain 27A23
Allergic reaction 27A24
Diabetic 27A25
156
Appendix Two Objectives of CBD as defined by the Association of Chief Ambulance Officers
The objectives of CBD are:
• To establish critical information from caller (telephone number, chief complaint, location, age, sex,
and conscious level).
• To identify dispatch code.
• To decide a Priority Level of the call.
• To offer pre-arrival instructions to the caller.
• To provide ambulance staff or the responder with more detailed information.
• To get medical help to every Priority “A” call within eight minutes.
Dispatch Categories (UK) as defined by the Association of Chief Ambulance Officers
Priority "A": An immediate life-threatening situation requiring urgent assistance. The objective
is to provide immediate aid to apply life saving skills supported by Paramedic
intervention.
Standard: To reach 75% of priority “A” cases within 8 minutes.
Priority “B” &
"C":
A serious condition which is not immediately life-threatening for example,
controlled haemorrhage. The objective is to provide Paramedic intervention as
soon as possible.
Standard: To reach 95% of cases within 14 minutes.
Dispatch Categories (US) as defined by King County, Seattle, USA, originators of CBD.
Category "A" An immediate life-threatening situation requiring urgent assistance. The objective
is to provide immediate aid by telephone advice, followed by rapid on scene
assistance.
Category "B" A serious condition which is not immediately life-threatening. The objective is to
provide intervention as soon as possible.
Category "C" Other non-serious or non-life-threatening conditions but which require
conveyance to hospital.
157
Appendix Three. Sample of recruitment letter.
Please Reply to: Dr M W Cooke Senior Lecturer A&E Department City Hospital Dudley Road Birmingham B18 7QH Tel 0121 507 5522 Fax: 01564 776140 E-mail [email protected]
02 June 1997 «Title» «Initials» «LastName» «JobTitle» «Company» «Address1» «Address2» «City» «State» «PostalCode» Dear «FirstName» Re: Safety of prioritisation of 999 calls I am undertaking some research relating to the safety of the new systems of prioritising 999 calls. This is being funded by NHS R&D. The main part of the study is related to clinical outcome of the various prioritisation categories. One portion of the study needs the opinion of experts on the system. These experts will all be A&E specialists who are active in pre-hospital care. The crunch- would you be prepared to be one of these experts? The work would involve review a set of criteria for the dispatch categories. You would be provided with the lists that the ambulance control assistant’s use and asked to mark those you consider that are under or over categorised. This would be simply done by use of two colours of highlighter pen. I would not expect it to take more than 45 minutes. Any other comments would be at your discretion. If you agree, I would ask that the papers are returned within three weeks of receipt. You would of course be acknowledged in the final report/ papers. If you could assist me then either just fax a copy of this letter back to me on 01564 776140 (no need for a cover sheet) with “YES” written below or phone my secretary on 0121 507 5522. If you would like to speak to me about it further before committing yourself, then call me on 07000 782377. Thanks for considering this Yours sincerely, Dr Matthew Cooke
158
Appendix Four- .Guidance for Study α & β.
Guidance for expert panel
How does the system work?
The control assistant (CA) determines which group the patient belongs to from the initial information received (for
example, abdominal pain, allergic reaction etc.).
They then look at the appropriate sheet for that condition and work from the top of the list (i.e. priority one
conditions) and work their way down the list, until they find a symptom/condition that fits the patient. It is
important to follow the list in this direction.
Example
If a patient has an allergic reaction of over 30 minutes duration they will not always go into priority “B”. If they had
any of the symptoms listed in Priority “A”, that category would be assigned. Therefore patients with over 30
minutes symptoms will only be assigned “B” if they are not unconscious, have no difficulty breathing or
swallowing, can talk full sentences, have no swelling in throat and have had no fainting.
What do the categories mean?
Priority “A” is the immediate response with a standard of 75% reached within 8 minutes.
Priority “B” has a standard of 14 minutes response. Patients in this category can be delayed whilst those in category
“A” are dispatched.
Priority “C” are those that are not emergencies and can have a delayed response (as yet not defined by time).
What do I do?
Please can you read through each page of the dispatch criteria.
As you read please assess whether you consider that the condition described is in the appropriate group.
Please mark those you consider in the incorrect group with the highlighter pen.
BLUE if you consider the group assigned is too low, i.e. the case is more urgent than stated.
YELLOW if you consider the group is too high, i.e. does not need that degree of urgency.
Add an ASTERISK * at the right hand end of the box, if you think that the categorisation is potentially dangerous.
If you want, you may add COMMENTS either in the left hand margin or on the reverse of the sheet. In particular,
please note any specific diagnoses that would result in mistriage.
Please return the sheets in the envelope provided. You can keep the pens!
What if I do not understand?
Please call Matthew Cooke on either 0121.507.5522 or 07000 782377
Thank You
159
Appendix Five. Instructions for study δ .
CBD opinion of control room staff.
Guidance for expert panel.
Why have I been selected?
A panel of control room staff has been selected at random to complete these forms. We
need to know the views of those using the system to ensure that the next version of CBD is
an improvement.
What do I need to do?
Please can you read through each page of the dispatch criteria.
As you read please assess the appropriate priority code for the condition (i.e. “A”, “B” or
“C”) and write this in the centre (Code) column. This code should be the priority YOU
believe the condition deserves, which may differ from what CBD states.
If you wish to add other comments, please write these in the right hand (Comments)
column. If there is insufficient space, please use the reverse of the page. I am especially
interested to hear of problems you have experienced with particular codes.
How do I return the form?
Please return the sheets and this form in the envelope provided. Place this sheet and the
forms in the envelope and seal it before giving to the duty officer. The contents of the
envelope will only be seen by the researchers at the University and not by any ambulance
service personnel. If possible, please return within three weeks of receipt.
What if I do not understand?
Please call Matthew Cooke on either 0121-507-5522 or 0468-198028.
Thank You
160
Appendix Six. Other sources of publications used in the literature search.
Internet Mailing Lists
Acad-AE-Med UK emergency medicine mailing list
EMD-L US based international ambulance dispatcher’s
list
EMED -L US based international emergency medicine list
EMS-L US based international prehospital care list
Other Internet-based searches
DARE (Database of Abstracts of Research
Effectiveness), Centre for Research
Dissemination, University of York
Key words - ambulance dispatch
NHS South West R&D, Wessex Institute Key words - ambulance dispatch
The Cochrane Library Key words - ambulance dispatch
Yahoo Health Key words - ambulance priority dispatch
Excite Key words - ambulance priority dispatch
Official document databases
Department of Health http://www.doh.gov.uk/
Audit Commission http://www.audit-commission.gov.uk/
Her Majesty's Stationary Office http://www.hmso.gov.uk/
National Association of Emergency Medical
Technicians
http://www.naemt.org/
National Academy of Emergency Medical
Dispatch
http://www.naemd.org/
National Institutes of Health http://www.nih.gov/
Non-cited journals: electronically searched
Pre-hospital Emergency Care http://www.hanleyandbelfus.com/journals/pec.ht
ml
Pre-hospital Immediate Care http://www.prehospimmedicare.com/
Emergency Medical Services http://www.emsmagazine.com/artindex.html
JEMS / Fire Rescue http://wwwdotcom.com/jems/ffnews/ffnews.html
Non-cited journals: hand searched
Journal of British Association for Immediate Care
Ambulance UK
911 Magazine
161
Appendix Seven. Proforma for articles undergoing expert appraisal in the
Literature Review.
NAME OF REVIEWER: .............................................…..……... Paper No............... A Systematic Review of Ambulance Emergency Call Prioritisation REVIEW PANEL PROFORMA All comments relate to the dispatch system element of the paper only Methodology Type of paper: (Please circle) Retrospective Original Research / Prospective Original / Research / Factual Literature Review / Literatur e Review with Opinion / Editorial / Letter
Yes No Don’t know
Not applicabl
e 1. Was there comparison to any other system? 2. Did the sample include an appropriate spectrum of patients?
3. Were any patients or groups excluded inappropriately?
4. Were the methods described sufficiently to permit replication?
5. Were relevant statistics utilised?
6. Was patient outcome at hospital arrival studied? 7. Was patient outcome at hospital discharge studied?
Critique
Yes No Don’t know
Not applicabl
e 1. Would the results be reproducible in any U.K. Ambulance Service?
2. Would results be reproducible in a system where prioritisation determines time of response?
3. Does this paper show that the dispatch system improves: i) clinical outcome ii) utilisation of Ambulance Service
4. Are there any particular requirements or special circumstances or limitations relating to this study?
162
NAME OF REVIEWER: .............................................…..……... Paper No............... Is there a statistical component that requires expert review? YES / NO Is there a cost effectiveness component that requires expert review? YES / NO General Comments 250 words maximum .................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................. ........................................................................................................................................................... Have you any suggestions as to other people or organisations with an interest in this area? ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ ..................................................................................................................................................................... Do you have any potential conflict of interest relating to any dispatch system? .......... ................................................................................................................................................................................................................................................................ .................................................................................................................................... Please attach extra sheets/information as required. Thank you for your participation. Please return the completed Profor ma to Pam Bridge, Project Officer:
either by Fax: - +44-121-414-3759 or by Air Mail post: Department of General Practice
University of Birmingham Medical School Edgbaston Birmingham B15 2TT
England.
163
Appendix Eight.. Articles undergoing expert appraisal in the Literature
Review.
Bailey ED, O’Connor RE, Ross RW. The use of an emergency medical dispatch system to
reduce the number of inappropriate scene responses made by advanced life support
personnel. SAEM 1997. Annual Meeting Abstracts #222 (Page 415).
Clark JJ, Culley L, Eisenberg MS, Henwood DK. Accuracy of determining cardiac arrest
by emergency medical dispatchers. Annals of Emergency Medicine 1994; 23:1022-1026.
Clark JJ, Larsen MP, Culley LL, Graves JR, Eisenberg MS. Incidence of Agonal
Respirations in sudden Cardiac Arrest. Annals of Emergency Medicine 1992; 21:12: 1464-
1467.
Cordi HP, Persse DE, Key CB, Pepe PE. Ability of a caller to 911 to correctly identify a
person as “Dead On Scene”. Prehospital emergency care 1997; 1(3) p.173.
Culley L, C lark JJ, Eisenberg MS, Larsen MP. Dispatcher-Assisted Telephone CPR:
Common Delays and Time Standards for Delivery. Annals of Emergency Medicine 1991;
20:4 362-366.
Culley L, Henwood DK, Clark JJ, Eisenberg MS, Horton C. Increasing the Efficiency of
Emergency Medical Services by Using Criteria Based Dispatch. Annals of Emergency
Medicine. 1994; 24:5 867-872.
Curka PA, Pepe PE, Ginger VF, Sherrard RC, Ivy MV, Zachariah BS. Emergency Medical
Services Priority Dispatch. Annals of Emergency Medicine 1993; 22:11 46-51.
Eisenberg MS, Carter W, Hallstrom A, Cummins R, Litwin P, Hearne T. Identification of
cardiac arrest by emergency dispatchers. University of Seattle, Washington 1986; 4:4 299-
301.
Eisenberg MS, Hallstrom AP, Carter WB, Cummins RO, Bergner L, Pierce J. Emergency
CPR instruction via telephone. American Journal of Public Health1985; 75:47-50.
Herlitz J, Bang A, Isaksson L, Karlsson T. Outcome for patients who call for an ambulance
for chest pain in relation to the dispatchers initial suspicion of acute myocardial infarction.
European Journal of Emergency Medicine 1995; 2:75-82.
164
Herlitz J, Bang A, Isaksson L, Karlsson T. Ambulance dispatchers estimation of intensity of
pain and presence of associated symptoms in relation to outcome in patients who call for an
ambulance because of acute chest pain. European Journal of Cardiology 1995; 16:1789-
1794.
Hu SC, Kao WF, Tsai J, Chern CH, Yen D, Lo HC, Lee CH. Analysis of prehospital ALS
cases in a Rural Community. Chinese Medical Journal. (Taipei). 1996; 58: 171-176.
Key CB, Persse DE, Pepe PE, Cordi HP, Ginger VF, Kimball KT. Safety of first-responder
only utilisation for motor vehicle incidents when the 911 caller is unable to answer standard
medical priority dispatch questions. Academic Emergency Medicine. 1997; 4:5 Abstract
No. 220 (page 414).
Lagaert L, Calle P, Vanhaute O, Buylaert W. How early and accurate are the calls for out of
hospital Cardiopulmonary Arrest (CPA) in Gent? Abstract of a poster at
“RESUSCITATION 96” in Seville 1997.
Lammers RL, Roth BA, Utecht T. Comparison of Ambulance Dispatch Protocols for Non-
traumatic Abdominal Pain. Annals of Emergency Medicine 1995; 26:5 579-589.
Meron G, Frantz O, Sterz F, Mullner M, Kaff A, Laggner AN. Analysing calls by lay
persons reporting cardiac arrest. Resuscitation 1996; 32:23-26.
National Association of Emergency Medical Services Physicians 1995. Abstracts of
Scientific papers. Prehospital and Disaster Medicine 1995; 10:4 Supp, 51-73.
Palumbo L, Kubincanek J, Emerman C, Jouriles N, Cydulka R, Shade B. Performance of a
System to Determine EMS Dispatch Priorities. American Journal of Emergency Medicine.
1996; 14:3 388-390.
Slovis CM, Carruth TB, Seitz WJ, Thomas CM, Elsea WR. A Priority Dispatch System for
Emergency Medical Services. Annals Emergency Medicine. 1985; 14:11 1055-1060.
Sramek M, Post W, Koster RW. Telephone triage of emergency calls by dispatchers: a
prospective study of 1386 emergency calls. British Heart Journal. 1994; 71: 440-445.
165
Appendix Nine Data collection Proforma
ID: Patient surnam e:
Patient forename:
Age: Sex: Patient Home Postcode:
Home incident:
If no, incident Postcode:
Date 999 call:
Patient Information Sheet
A&E Notes
Amb Call sign: Hospital: Amb Attendant No: A&E Number: Amb Assistant No: Triage Nurse Name Code: Incident Dispatch CBD Code:
A&E Triage category:
WMAS Case No: A&E Triage - Reason urgency:
Time 999 call: Most Senior Dr: Time arrival on scene: A&E Monitoring:
Time left scene: A&E Urgent drug treatment: Time arrival A&E: A&E other urgent
intervention:
Original 999 call time: A&E other reason urgency Attendance time (secs) A&E Airway clear: Time at A&E after 999 call (secs)
A&E Breathing present:
Airway clear: A&E AVPU: Breathing present: A&E Most urgent action AVPU A&E Outcome: Duration of complaint (hrs): A&E Diagnosis: On scene chief complaint: Amb. crew CBD code. Registrar PHC Monitoring Registrar dispatchers expected
code:
PHC Spine immobilisn: Registrar ‘on diagnosis' code: PHC Fluid resusc: Registrar reason: PHC Drugs: PHC other intervention: Ambulance Control PHC other reason urgency: Dispatcher code: PHC most urgent action Communicat ion problem: If other, comm problem descr: MWC On scene CBD code: PAS A&E CBD code: Hospital Number: Days in-patient Independent Days ITU: Independent ‘on diagnosis’ code:
Reason independent code:
166
Appendix Ten Recommendations for modifications to CBD.
a) CBD system issues
Category Notes Recommendation
Cardiac Arrest The period of cerebral hypoxia causes a fit in the early stages of a cardiac arrest.
One of three cases of stroke also resulted in under-triage because it presented as a fit, which had stopped although the patient was still deeply unconscious.
Fits that are continuing or when the patient is unresponsive to be classified as a Category “A”.
Other under-triaged cases of cardiac arrest were recorded as “decreased level of consciousness” and “sick - third party caller”. Third party callers may have insufficient information and in such cases decisions should err on the side of safety.
The default for unknown or decreased conscious level must be an “A” response.
The two other under-triaged patients with cardiac related problems resulting in an alert, related to a faint and a fall in elderly men.
Consider separating faint and fall according to age to allow a higher prioritisation in the older age group where a medical cause is more likely.
Trauma CBD(UK) fails to detect serious head injuries in trauma victims
Misclassification of RTAs appears to be related to CBD (UK) using “mechanism of injury” rather than “conscious level” as the prime-sorting field.
RTAs should default to Category “A” unless there is definite evidence that everyone is conscious.
CBD(UK) classifies a fall from over 20 ft. as a Category B, whereas ATLS81 teaches that this is a high-risk injury
A different definition for children (for example, three times their height) may be appropriate.
The final trauma case was initially described as a minor bump to the head and therefore categorised “C”. This patient later developed fitting.
Only those head injuries with a clearly identified low energy accident resulting in minor wounds with no risk factors85 should be ascribed to Category “C”.
167
Burns Only two burn cases featured in this “alert” study and both were under-triaged. National Burns guidelines define shock cases as 10%+ for children and 15%+ for adults99.
CBD (UK) guidelines should be brought into line with National Burns guidelines. This presumes that such an estimate can be made over the phone.
Bleeding Two patients had uncontrolled external haemorrhage. One case was from a third party caller and again demonstrates the need for an “A” classification when there is insufficient information.
Uncontrolled external haemorrhage should be a new “A” category.
A discrepancy in coding according to how the dispatcher enters the CBD system was noted. If coded by chief complaint “Bleeding", priority “B” would be assigned whereas vaginal bleeding in the chief complaint “Gynaecology” generates an “A” priority.
This inconsistency relating to how the dispatcher enters the system should be removed.
Unconscious If all cases with decreased conscious level (either P or U on AVPU scale) were classified as “A", this would have detected at least 11 of the total 29 misclassified “alert” calls.
All cases with decreased conscious level should be classified as “A”.
168
b) Dispatcher training issues
Category Notes Dispatcher training should include
Cardiac Arrest The period of cerebral hypoxia causes a fit in the early stages of a cardiac arrest.
Consider the possibility of a fit as presentation of hypoxia/cardiac arrest
If the fit is continuing , consider this as unconscious.
If the fit has stopped, check conscious level.
Other under-triaged cases of cardiac arrest were recorded as “decreased level of consciousness”.
The default for unknown or decreased conscious level must be an “A” response.
The two other under-triaged patients with cardiac related problems resulting in an alert, related to a faint and a fall in elderly men.
Consider whether an older person may have collapsed rather than fainted
Trauma Misclassification of RTAs appears to be related to the use of “mechanism of injury” rather than “conscious level” as the prime -sorting field.
If there is a possibility of anyone being unconscious or having difficulty in breathing use an “A” category.
CBD(UK) classifies a fall from over 10 ft. as a Category “B”, whereas ATLS81 teaches that this is a high-risk injury.
Remember a smaller fall is dangerous in children.
A patient received minor bump to the head and was therefore categorised “C”. This patient later developed fitting.
If there was a high force or any unconsciousness/amnesia or a large cut then do not use Category “C”.
Bleeding A discrepancy in coding according to how the dispatcher enters the CBD system was noted. If coded by chief complaint “Bleeding", priority “B” would be assigned whereas vaginal bleeding in the chief complaint “Gynaecology” generates an 'A' priority (Table 7).
Use the gynaecology code in preference to the bleeding code.
Unconscious If all cases with decreased conscious level (either P or U on AVPU scale) were classified as “A", this would have detected at least 11 of the total 29 misclassified “alert” calls.
If the person cannot be confirmed to be alert or responding to a command, classify as unconscious.
All Third party callers may have insufficient information and in such cases decisions should err on the side of safety.
Presume the patient is unconscious if the caller cannot give details.
169
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