Lecture 7: Incorporating Human Factors
Engineering into Clinical Management
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Outline
Clinical Engineers (Historical) Human Factors/ Ergonomics
Device Limitations Use of Human Capabilities Environmental Factors Culture HFE Techniques
Failure Mode and Effect Analysis Heuristic Evaluation
Conclusion
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Clinical Engineers (Historical) Proliferation of new medical technologies Need for engineering experts in medical
instrumentation and devices Patient safety related activities Need for more than the maintenance and repair
of equipment Incident investigator of equipment related
injuries Adherence to regulatory codes and standards
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Clinical Engineers in Health Care Today “ A Clinical Engineer is a professional who
supports and advances patient care by applying engineering and managerial skills to healthcare technology” (Gebara, R.)
Project Management Technology Assessment Technology Management Risk Management Standards Compliance Training/Education
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Driving Forces for Patient’s Safety It’s the right thing to do for our patients The IOM Reports and Recommendations JCAHO Standards National Patient Safety Goals Safe Medical Device Act Financial implications of errors Public awareness and concern
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How can Clinical Engineers Contribute to Patient’s Safety? Use Human Factors Engineering research
to evaluate medical devices and investigate medical incidents
Identify critical safety initiatives and provide a short term solutions
Collect data for future planning and improvements aiming for optimal product design and quality
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Human Factors / Ergonomics
Human factor is defined as “the study of how humans accomplish work-related tasks in the context of human-machine system operation, and how behavioral and non-behavioral variables affect that accomplishment” – Meister (1989)
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Human Factors Engineering / Ergonomics An engineering discipline that looks to
understand the relationship between people and the systems that surround them to understand and optimize how people use and interact with technology
Avoid reliance on memory Use forcing functions Avoid reliance on vigilance Simplify key processes Standardize work processes Design systems with feedback and monitoring
mechanisms
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First Loop: Human-Machine System
Display
Controls
SensorySystem
MotorSystem
BrainComplexSystem
Human Machine
Interface 335
Human Factors Engineering / Ergonomics Mitigates and reduces errors in multiple high
reliability organizations (HRO) Predicts and provides an understanding of
human performance in complex environments Discovers underlying systemic factors that lead
to error Provides a framework for medical device
evaluation Identifies areas to improve patient safety
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High Reliability Organizations: Strong HFE Applications Nuclear Power Plants Air Traffic Controller Flight Deck on an Aircraft Carrier
Crew Resource Management Space Shuttle Hospitals
Emergency Departments Operating Rooms Intensive Care Units Centralized Telemetry Units
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HFE: Causal Factors
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Device Limitations
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Manipulated Display Design Variables
Location: Color Dimensionality: planar/perspective Motion: motion/stationary Intensity: dim/bright Coding: physical dimensions (size,shape) Modality: visual/auditory Content: information & structure
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Four (4) Categories of Display Design Principles1. Perceptual Consideration
• Avoid absolute judgment requirements, e.g. identification of specific sound level
• Support top down processing• Exploit redundancy gain• Maximize discriminability
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Four (4) Categories of Display Design Principles
2. Mental Model Consideration• Pictorial realism, e.g. orientation• Movement compatibility, e.g. direction• Ecological consistency
3. Attention Consideration• Minimize information processing cost• Proximity Compatibility (spatial compatibility)• Multi-channel processing
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Four (4) Categories of Display Design Principles
4. Memory Consideration• Support prediction• Exploit knowledge in the world, reduce
demands for knowledge in the head. E.g. recognition.
• Ensure consistency
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Stimulus-Response Compatibility
Compatibility between displayed information and method of response or control
Static sense: Compatibility between a display location and the location of the response
Dynamic sense: Compatibility between display movement and movement involved in the response
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Locational Compatibility
We have natural tendency to move or orient towards source of stimulation in environment—infants will orient to new pictures, new faces
Put the controls where the displays are – users want to move towards the source of stimulation
So why not put the control and the display in the same location? colocation principle
A touch screen takes this idea to the limit Elevator buttons Can’t always do that so, put controls right next to
displays (as close as possible)
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Stovetops Revisited
More compatible mappings between stimulus display and response means fewer mental operations, transformations from display to response
Norman called “natural mappings”
Co-location Poor compatibility348
Organizing S-R Compatibility
S-R Compatibility
Static Dynamic
Colocation(Locational
Compatibility)
Congruence MovementCompatibility
MovementProximity
Rules (Simplicity) or Stereotypes can be used to improve static or
dynamic compatibility
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Movement Compatibility
Compatibility in the dynamic sense: Compatibility between display movement
and movement involved in the response Typically movement of the control should
correspond to the movement in the display
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Movement Compatibility
Sometimes this can’t be done for practical reasons, however
There are common ways to show an increase: move a control up, to the right, forward, or clockwise
These types of common conventions are called population stereotypes
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Movement Proximity (Warrick’s principle)
Place moving control close to moving display
Principle of movement proximity
Better than:
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Errors Reason’s representation of the
relationship between decision errors, and the final unsafe acts--which produce local triggers via mediating factors
Mediating factors may be thought of as resident pathogens
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Use of Human Capabilities
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Vision / Visual
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Auditory
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Cognition vs. Perception
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Human Information Processing Model
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Environmental Factors
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Culture
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HFE Techniques
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Failure Mode and Effect Analysis
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Failure Mode and Effect Analysis (FMEA)
Is a tool for preventing failures. It is a way to identify the failures, causes, effects, and risks within a design or process and eliminate or reduce them.
Is a procedure for developing new designs or processes. Is the diary (documented evidence) of the design, the process
and the service. Is a systematic way of evaluating, tracking, and updating
designs and process development. Is a team-based approach.
- Palady, P. (1998) -
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5 Elements of an FMEA
1 Planning the FMEA
2 Failure Modes Effects Causes
3 Occurrence Severity Detection
4 Interpretation
5 The Follow Through
- Palady, P. (1998) -
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5 Elements of an FMEA
1. Planning the FMEA
2. Investigating the Failure Modes, Effects, and Causes
3. Determining the Occurrence, Severity, and Detection
4. Interpretation the FMEA
5. The Follow Through
- Palady, P. (1998) -
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1. Planning the FMEA
Planning the FMEA involves selecting the FMEA project and the team composition.
Select a project that has the greatest potential for quality payback to the company and its customers.
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2. Investigating the Failure Modes, Effects, and Causes
We should ask ourselves these 3 questions,
How could it fail? (Failure Mode) Why does it fail? (Causes) What happens when it fails? (Effects)
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3. Quantifying Severity, Occurrence, and Detection
We will use a rating scales to quantify severity, occurrence, and detection.
As a general rule, when rating the Occurrence, Severity, and Detection in FMEA, the bigger numbers are bad and the small numbers are good.
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4. Interpreting the FMEA
There are two common ways of analyzing and interpreting the FMEA. These are the:
Risk Priority Numbers (RPN)Area Chart
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5. The Follow Through
FMEA requires applications of other supporting quality tools. Some of these tools are Control Charting (SPC) and Design of Experiment (DOE).
Data must be analyzed using statistical methods at each step of the FMEA.
Little or no benefits can be expected from the FMEA without follow through.
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Benefits of FMEA
Cost savings: development cost Identification of safety concern for validation Serve as a guide for more efficient test
planning Improve customer satisfaction Track design changes and provide updates.
- Palady, P. (1998) -
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Benefits of FMEA
Minimize engineering changes Minimize unforeseen events or uncertainties
when designing or validating a process Minimize unnecessary controls in the process
- Palady, P. (1998) -
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Definitions
Failure is the inability of a design or process to perform based on its function. This is usually referred to as the problem, error, concern or challenge.
Potential Failures are failures that can happen on the design or process when being used by our customer.
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Definitions
Potential Effect are outcomes from potential failures which can either be mild or severe when the customer interacts with the potential failures of the product.
Failure Mode is the physical description of the manner in which an expected function is not achieved.
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Characteristics of a Failure Mode Each failure mode has potential effects.
These potential effects can lead to problems for our customers.
It is important to determine the root cause(s) of a failure mode. The root cause is the one that points the way toward preventive and/or corrective action of a failure mode.
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Examples of Failure Modes
Oversized/Undersized packaging Discoloring Misalign pin Seal leakage Wrong invoice Corroded material
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Identifying the Root Cause
The Levels of Causes represent a sequence of causes that leads to the failure mode. The lowest level is called the root cause.
Some failure modes will have fewer or more levels of causes. The important thing is to pursue the root cause.
Detailed investigation and analysis has to be performed on failure modes.
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Levels of causes of a failure mode using a flashlight as an example
Level 1 Level 2 Level 3
Failure Mode First Level Cause Root Cause
A Flashlight did not light
Light Bulb is not
working
Filament inside the bulb is broken
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Identification of Failure Mode As an exercise, let us enumerate the potential failure modes of an ordinary ballpoint pen and identify its possible root cause(s) and effects. Potential Failures : Ink blots
Possible Root causes of failure: Ink is too wet
Ink cartridge is defective
Ball point is too loose
Possible Effects: Dirty and ruin things
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Determining the Severity, Occurrence, and Detection.
Severity is evaluated based on the effect of the failure mode to the customer.
Occurrence is evaluated based on how often a failure mode or its cause happens.
Detection refers to the chance of catching the problem before we give it to the customer.
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Severity
This is a rating indicating the seriousness of the effect of the potential failure mode
There is a direct correlation between effect and severity
- Stamatis, D.H. (1995) -
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Occurrence
This is also referred to “Frequency”. This is the rating value corresponding to the
estimated number of frequencies and/or cumulative number of failures that could occur for a given cause over the life of the design / over a given quantity of parts produced with the existing controls.
- Stamatis, D.H. (1995) - 382
Detection
This is the rating corresponding to the likelihood that the proposed design controls / current process controls will detect a specific root cause of a failure mode before the part is released for production / the part leaves the manufacturing area.
- Stamatis, D.H. (1995) -
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Quantifying Severity, Occurrence, and Detection
We will use a rating scale from 1 to 10 to quantify severity, occurrence, and detection.
As a general rule, when rating the Occurrence, Severity, and Detection in FMEA, the bigger numbers are bad and the small numbers are good.
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Severity Scale
Rating Criteria: A failure could…
10 Injure a customer or employee
9 Be illegal
8 Render the product or service unfit for use
7 Cause extreme customer dissatisfaction
6 Result in partial malfunction
5 Cause a loss of performance likely to result in a complaint
4 Cause minor performance loss
3 Cause a minor nuisance; can be overcome with no loss
2 Be unnoticed; minor effect on performance
1 Be unnoticed and not affect the performance
Bad
Good
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Occurrence Scale
Rating Time Period Probability
10 More than once per day 30%
9 Once every 3–4 days 30%
8 Once per week 5%
7 Once per month 1%
6 Once every 3 months .03%
5 Once every 6 months 1 per 10,000
4 Once per year 6 per 100,000
3 Once every 1 – 3 years 6 per million
2 Once every 3 –6 years 3 per 10 million
1 Once every 6 –100 years 2 per billion
Bad
Good
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Detection ScaleRating Definition
10 Defect caused by failure is not detectable
9 Occasional units are checked for defects
8 Units are systematically sampled and inspected
7 All units are manually inspected
6 Manual inspection with mistake-proofing modifications
5 Process is monitored (SPC) and manually inspected
4 SPC used with an immediate reaction to out of control conditions
3 SPC as above with 100% inspection surrounding out of control conditions
2 All units are automatically inspected
Bad
Good
1 Defect is obvious and can be kept from affecting customer
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Twelve Basic Items in an FMEA Worksheet Heading Parts or Process Failure Modes Effects Causes Controls
Severity Occurrence Detection RPN Recommendations Status
Design FMEA WorksheetDFMEA Analysis
Project: _____________________ Team : _____________________
Date ___________ (original) ___________ (revised)
Item or Component
Potential Failure Mode
Potential Effect (s) of Failure
Potential Cause(s)
Current Controls R
PN Recommended
Action
Responsibility and
Target Date Action Taken
Sev
erity
Occ
urre
nce
Det
ectio
n
RP
N
“After”
Sev
erity
Occ
urre
nce
Det
ectio
n
Total Risk Priority Number = “After” Risk Priority Number =
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DFMEA Analysis
Project: _____________________Team: _____________________Date ___________ (original)
___________ (revised)
Item or Process
Step
Potential Failure Mode
Potential Effect (s) of Failure
Potential Cause(s)
Current Controls R
PN Recommended Action
Responsibility and
Target Date Action Taken Sev
erity
Occ
urre
nce
Det
ectio
n
RP
N
“After”
Sev
erity
Occ
urre
nce
Det
ectio
n
FMEA is a “Three-for-One” Tool – FMEA is a “Three-for-One” Tool – Cause and Effect, Pareto, and Countermeasure Cause and Effect, Pareto, and Countermeasure
Matrix!Matrix!
Cause & Effect Analysis of
Design/Process Potential Failures
Cause & Effect Analysis of
Design/Process Potential Failures
Pareto Analysis – Failure Priorities
Pareto Analysis – Failure Priorities
Countermeasure Identification and
Impact Assessment
Countermeasure Identification and
Impact Assessment
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Pareto Chart
All causes do not contribute equally to
a potential failure mode.
Approximately 20% of the listed causes
contribute to approximately 80% of the failure mode
- Palady, P. (1998) -
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HFE Techniques
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Jacob Nielsen 10 Usability heuristics
1. Visibility of system status2. Match between system and the real world3. User control and freedom4. Consistency and standards5. Error prevention6. Recognition rather than recall7. Flexibility and efficiency of use8. Aesthetics and minimalist design9. Help users recognize, diagnose and recover from
errors10. Help and documentation
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Shneiderman 8 golden rules
Strive for consistency Enable frequent users to use shortcuts Offer informative feedback Design dialogue to yield closure Offer error prevention and simple error handling Permit easy reversal of actions Support internal locus of control Reduce STM load
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Conclusion
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Mini-Case
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Mini-Case: get a host hospital and do the following: Identify human factor issues in clinical
management: Hospital organizational Hospital information flow and handling Equipment procurement and vendor management Equipment and inventory control management
Use FMEA to analyze and resolve the human factor issues for each clinical management area
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Mini-Case: choose a biomedical equipment Identify and analyze the four design display
variables in the equipment Identify usability issues in the equipment by
using usability heuristics Make recommendations on the identified
issues or problems using usability heuristics
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Reference
Rani GebaraBeaumont Services Company3601 W. 13 Mile RdRoyal Oak, MI 48073Phone: 248-551-7324E-mail: [email protected]
FMEA book GET FROM OPAC
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