clinical instrumentation

7/29/2019 Clinical Instrumentation

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Clinical Instrumentation

Contents

1. Classification of Medical Equipment

2. Management of Medical Equipment

3. Electrical safety of Medical Equipment

4. Transducers in Medical Applications

5. Basic Principal of the Operation of

i. Surgical Diathermy

ii. ECG Machine

iii. Defibrillator

iv. ICU Ventilator

v. Anaesthetic Machine

vi. Hemo Dialysis Machine

vii. Pulse Oxymeter

viii. EEG

ix. EMG

Classification of Medical equipment-

Medical equipment is machinery designed to aid in the diagnosis or treatment of medical

problems. The term medical devices (Equipment) includes everything from highly

sophisticated computerized medical equipment down to simple wooden tongue depressors. The

intended primary mode of action of a medical device on the human body, in contrast with that of

medicinal products, is not metabolic, immunological, or pharmacological.

There are several methods to name the medical equipment.

i. Bio-Medical Equipmentii. Electro-medical Equipment

iii. Medical Instrument

iv. Clinical Instrument

Definitions for Medical Equipment

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Definition in Europe:

Any instrument, apparatus, appliance, material or other article, whether used alone or in

combination, including the software necessary for its proper application intended by the

manufacturer to be used for human beings for the purpose of:

- diagnosis ,prevention ,monitoring,treatment or allevation of disease,

- diagnosis,monitoring,treatment,alleviation of or compensation for an injury or handicap

- investigation,replacement or modification of the anatomy or a physiological process,

- control of conception ,and which does not achieve its principal intended action in or on

the human body by pharmacological ,immunological or metabolic means, but which may

be assisted in its function by such means.

Definition in USA :(Food and Drug Administration- FDA)

Amedical device is an instrument,apparatus, implement, machine, contrivance, implant, in vitro

reagent, or other similar or related article, including a component part, or accessory which is:

-recognized in the National Formulary,or the United States Pharmacopoeia ,or any supplement to

them.

- intended for use in the diagnosis of disease or other conditions, or in the cure, mitigation,

treatment, orprevention of disease, in man or other animals, or

- intended to affect the structure or any function of the body of man or other animals, and which

does not achieve any of its primary intended purposes through chemical action within or on the

body of man or other animals and which is not dependent upon being metabolized for the

achievement of any of its primary intended purposes.

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http://en.wikipedia.org/wiki/Food_and_Drug_Administrationhttp://en.wikipedia.org/wiki/Toolhttp://en.wikipedia.org/wiki/Apparatushttp://en.wikipedia.org/wiki/Machinehttp://en.wikipedia.org/wiki/Implanthttp://en.wikipedia.org/wiki/In_vitrohttp://en.wikipedia.org/wiki/Reagenthttp://en.wikipedia.org/wiki/Diagnosishttp://en.wikipedia.org/wiki/Diseasehttp://en.wikipedia.org/wiki/Curehttp://en.wikipedia.org/wiki/Mitigationhttp://en.wikipedia.org/wiki/Treatmenthttp://en.wikipedia.org/wiki/Preventionhttp://en.wikipedia.org/wiki/Metabolismhttp://en.wikipedia.org/wiki/Food_and_Drug_Administrationhttp://en.wikipedia.org/wiki/Toolhttp://en.wikipedia.org/wiki/Apparatushttp://en.wikipedia.org/wiki/Machinehttp://en.wikipedia.org/wiki/Implanthttp://en.wikipedia.org/wiki/In_vitrohttp://en.wikipedia.org/wiki/Reagenthttp://en.wikipedia.org/wiki/Diagnosishttp://en.wikipedia.org/wiki/Diseasehttp://en.wikipedia.org/wiki/Curehttp://en.wikipedia.org/wiki/Mitigationhttp://en.wikipedia.org/wiki/Treatmenthttp://en.wikipedia.org/wiki/Preventionhttp://en.wikipedia.org/wiki/Metabolism


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The Definition of Global Harmonization Task Force for medical devices ( GHTF document

SG1/N029R11).

Medical device means any instrument, apparatus, implement, machine, appliance, implant, in

vitro reagent or calibrator, software, material or other similar or related article, intended by the

manufacturer to be used, alone or in combination, for human beings for one or more of the

specific purposes of:

Diagnosis, prevention, monitoring, treatment or alleviation of disease

Diagnosis, monitoring, treatment, alleviation of or compensation for an injury

Investigation, replacement, modification, or support of the anatomy or of a physiological

process

supporting or sustaining life

Control of conception

Disinfection of medical devices

providing information for medical purposes by means of in vitro examination of specimens

derived from the human body and which does not achieve its primary intended action in or on the

human body by pharmacological, immunological or metabolic means, but which may be assisted

in its function by such means.

Basic Categories of Medical Equipment.

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1. Physiological Test and the other Test Equipment for Patients

ECG,EEG,EMG, Pulse Oximeter,Blood Gas Analyzer, Spirometer,

2. Patient Monitoring Systems

ECG Monitor, IBP Monitor, Pulse Oximeter,Foetal monitor,

3. Laboratory Equipment

Flame photometers, Spectrophtometers, Auto Analyzers,Electrolyte Analyzers,Blood

Cell counters, Haematocrit Centrifuges , Tissue processors,Microscopes, Centrifuges

etc.

4. Medical Imaging Equipment

MRI Scanner,CT Scanner,PET,Ultra Sound machines,X-ray machines, Gamma Camera

4. Theraputic Equipment

Infusion Pumps, Syringe Pumps, Medical laser, Physio thrapy equipment like Muscle

Stimulators, IR Lamps, and Surgical Diathermy, Dialysis Machine,

Management of Medical Equipment

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With the development of electronic technology, medical equipment technology has made a

remarkable progress in the recent past. The development of new materials and researches of

medical technology too have been contributed towards it. At present , many highly sophisticated

medical equipment has been used in medical institutes.

Therefore it is very important to have a proper management system to ensure the equipments

reliability and the safety.

Reliability

The Equipment shall be perfectly accomplished with its supposed purposes- diagonostic or

theraputic.

Safety

The equipment shall be operated without any risk of life for both operator and the patient

Reliability and safety is related to each other and should be considered in development, design,

manufacture, sale and operation stages of a medical equipment. After an equipment dispatched to

user its performance and function will gradually decrease with the time, i.e . reliability and safety

decreases with the time.

In addition, according to the statistics available, many equipment failures occurs resulting from

their operation without timely maintenance and from poor handling.

.

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Medical Equipment Failures

Any equipment, medical or not, would fail during its life cycle ,eventhough they are properly

used and maintained. However, if we know how the equipment would be failed on its life cycle

in anticipation,we would be able to take an efficient countermeasure before it occurs. As a result

the equipment would continuously be operated in working order for a long time.

Failure Rate

When N0pieces of equipment or of components are operated for definite

hours ,t,in the same environment each other ,some pieces ,n, out of them will fail

certainly .

Here survived equipment or components, N, is represented as given below.

N N0 n

And then failure Rate is defined ,

( dn/dt)/ N

Equipment failures (breakdowns, malfunctions, unsafe) can be categorized into three stages on

the basis of their rate of occurrence: they areperiod of initial failures, period of random failures

and period of worn-out failures .

Failure Rate Curve

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Above figure shows a failure rate curve of equipment and this curve are called as bathtub curve.

The bathtub curve, does not depict the failure rate of a single item, but describes the relative

failure rate of an entire population of products over time.

The failure rate is high during initial stages. This may occur when the equipment is justmanufactured due to material defects, design blunders, errors in assembly, etc. However such

defects may not be detected by the user because such short comings are often observed and

rectified during the examinations and inspections after manufacturing in the factory or at the

installation stage.

Afterwards, the state of the equipment would be stabilized, and the equipment failure is rare

during this period. In this period, the failure would occur at random. This period can be said as

period of young age to middle age if compared to the human being.

The last part of the curve shows the equipments old condition. Here , the failure rate starts risingagain resulting from the degradation, wear-out, or break-down of the components inside the

equipment with the time. However, during this period, the failure rate can be reduced by

replacement of old and /or faulty components, and their proper adjustments. Then the life span ofequipment can be increased thus. When many failures appear at a time or failures appear

repeatedly , the budget expenditure on repairs increases and equipments reliability and safety

cannot be kept anymore, that indicates the end of equipments life.

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Causes of Equipment Failures

1. Design Failures

Manufacturers always try to produce high quality equipment even in the process of designing

electronic circuits and components. But, a few cases of equipment failure due to poor designsuch as improper choice of components, parameter of electronic circuit would appear after its

dispatch to the user.

Failures due to Careless Storage and Transport.

Poor storage of equipment such as undue long storage, improper packaging and unfavorableenvironmental conditions may cause of equipment failure. Excessive vibrations and mechanical

shocks may also cause of failures.

Initial Failures

This failure would appear in the initial use of equipment. Poor circuit design, improper choice of

components ,faults of producing process etc., could cause this failure. We may consider that ifthe equipment becomes fault without any mishandling within one year after its dispatch to the

clinical field , it could be treated as initial failure.

4. Random Failures

This is an equipment failure which would occur at random. We often experienced that theequipment was suddenly failed even though it had been operated in sufficient handling. The

number of break downs during the random failure is rare. This is mostly due to faults in

electronic components on the printed circuit board (PCB ) such as transistors, ICs ,resistors andcapacitors ,etc.

5. Worn-out Failures

The equipment becomes old with the passage of time and faults appear elsewhere that cause

further deterioration of smooth working of the equipment. Finally, the equipment becomes

unserviceable.

6. Failures due to Inadequate Maintenance.

In order to keep the equipment in good condition ,proper function, safety and supposed life

span ,the preventive or regular maintenance should frequently be carried out in accordance with

manufacturers instructions . About 75% out of overall failure is due to improper or inadequatemaintenance.

7. Failures due to Mismanagement of Repairs

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Unqualified repairing techniques could give another cause of equipment failure in its future, even

if it is repaired for the time being. Therefore it is necessary to obtain the service of fully qualified

and well trained technicians . Quality controlling of the repairs is also a important factor. Itshould be remembered that mismanagement of repairs could cause another damage to the

equipment which even manufacturer cannot guarantee to restoration of it.

8. Failures due to Careless Handling

Carelessness or rough handling can cause improper operation of the equipment or fault and

breakdown in it.

9. Failures due to Environmental Stress

Hostile working environmental conditions like lack of air-conditioned room, dust free areas,

under direct sunlight etc., could be the causes of equipment failure; fluctuations in voltage supply

and water quality also could be the causes of it. These environmental conditions are not to be acause of equipment failure ,but also great enemy of the keeping equipments expected life span .

Any of the above factors may lead to either sudden breakdown of the equipment or slow

degradation in performance. The failure may manifest itself in the deterioration of the stability

,reproducibility ,accuracy and overall performance.

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Medical Equipment Management System

The running of medical equipment should be continuosly and synthetically be managed during

its life cycle ; from purchasing upto condemning and disposing.

1. Need Assessment

A comprehensive assessment should be performed prior to the purchasing. It should be carefully

discussed with the Clinicians ,physicits,Biomedical Engineers and The administration, whether a

new equipment is really needed and on what basis ( Replacement of an old equipment or service

expansion),working conditions and capabilities of available equipment, available infra-structure

facilities and necessary modifications etc.

2. Purchasing

Technical specifications and purchasing conditions should be prepared according to the need

assesment.In this stage,the purpose of the equipment, its technical abilities financial limitations,

and safety features etc shall be discussed. A proper maintenance plan shall also be included and

the technical capabilities of supplier shall also be considered. If you have a machine of a certain

make , maintenance can be made easier by purchasing a second machine of the same make. This

also reduces the cost of training etc. However ,this leads to a monopoly of one manufacturer will

have negative effects if he fails .

3. Installation and Testing

Installation and Testing should be done by properly trained and qualified engineers and

technicians from manufacturer or his agents. Records should be kept on performance, safety and

functions. The supervision of clinician is necessray for this stage.

4. Corrective and Preventive Maintenance

Very important to improve the life span, performances and safety of the equipment . All the

calibrations and maintenance works should be carried according to the manufacturers

instructions.

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5. Clinical Use

All the componenet of medical equipment management system are linked to clinical use by one

or another way as all the factors affect the clinical use.

6. Disposing

When many failures appear at a time or repeatedly fails , the budget expenditure on repairs

become no economical and the safety and the reliability cannot be guranteed. Then the equiment

should be disposed. In this case ,all necessary data from technical departments such as repair

cost, and from clinical departments on reliability and safety ,shall be obtained for the justification

of the dispose.

If there is any regulations for the disposing of equipment, for the safety of public, all those shall

be carefully followed.

7. Training

Both technical and clinical staff should be trained in order to avoid mishandling and for the

safety of the patient.

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clinical instrumentation

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