Human Factors in Medical Devices

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Human Factors in Medical Devices

• Alan Coulson
• Software Engineer
• LifeScan Scotland Ltd

2
Usability

• Design
• Examples
• Tools
• Summary

Toyota Prius gear stick
3
Design

• Objects and machines we use in everyday life must
  all be designed.
• Adding features often gives competitive edge in
  the marketplace, often at the expense of
  simplicity and usability.

An office water dispenser
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Design
5
Design
6
Design
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Human Error?
The following factors contributed to the
incorrect response of the flight crew 3.
They did not assimilate the indications on the
engine instrument display before they throttled
back the No. 2 engine

• People tend to blame others (or themselves) when
  things go wrong
• Hence the term human error
• Often, its bad design that leads people to make
  errors.

AAIB report into Kegworth Air Disaster Jan 1989
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Human Error?
Although there seems to be no question that the
EIS display on the Boeing 737 provides accurate
and reliable information to the crew, the overall
layout of the displays, do appear to require
further consideration. These factors should not
be ignored and the suitability of such new
displays for use by airline pilots should be
evaluated before they are brought into use.
AAIB report into Kegworth Air Disaster Jan 1989
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Medical example

• Therac 25
• Contributory factors
• Removal of redundancy on the user interface
• Poor software design and testing
• Poor error messages

http//neptune.netcomp.monash.edu.au/cpe9001/asset
s/readings/Therac-3.GIF
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Preventable Anaesthesia Mishaps

• Analysis of 359 mishaps resulted in
• 82 human error
• Equipment design was indictable many categories
  of human error
• 14 equipment failure
• Remaining could not be classified

• Cooper, Newbower, Long, McPeek, (1978)
• Critical Incident Technique adapted from the
  aviation industry

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Design
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Design

• Human errors in medical device use account for a
  large portion of medical errors
• Most of these errors are due to inappropriate
  designs for user interactions, rather than
  mechanical failures
• Zhang J., Patel, V. L., Johnson, T.R., Chung, P.,
  Turley, J.P 2005

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FDA

• FDA actively promote and require Human Factors
  in design of medical devices
• Do it by Design 1996
• Medical Device Use-safety Incorporating Human
  Factors Engineering into Risk Management, 2000
• Manufacturer and User Facility Device Experience
  Database - (MAUDE)
• (amazing how similar these reports are to AAIB
  reports!)

From http//www.fda.gov/cdrh/annual/fy2000/ohip/r
eduseerror.html
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Patient-use Medical Device
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Risk Management

• In the context of medical devices, FDA define a
  hazard as a potential source of harm arising from
• Medical treatment
• Device failure
• Device use

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Design and Evaluation Tools

• Fortunately there are some tools available to help

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Design and Evaluation Tools

• Fortunately there are some tools available to help

18
Design and Evaluation Tools

• How can these tools be used?
• In gathering requirements
• By designers and engineers
• By prospective purchasers

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Design and Evaluation Tools

• Heuristic Evaluation
• Cognitive Walkthrough
• Design Principles

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Tool 1 Heuristics

• Visibility of system status
• Match between system and the real world
• User control and freedom
• Consistency and standards
• Error prevention
• Recognition rather than recall
• Flexibility and efficiency of use
• Aesthetic and minimalist design
• Help users recognize, diagnose, and recover from
  errors
• Help and documentation
• Nielsen http//www.useit.com/papers/heuristic/heu
  ristic_list.html

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Heuristic Evaluation

• Rate the usability of an object according to the
  heuristics

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Heuristic Evaluation

• Rate the usability of an object according to the
  heuristics
• E.g. This example fails heuristic 2 (match
  between system and real world)

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Heuristic Evaluation Exercise

• Make up your own heuristics
• Especially on safety
• Make up your own scale
• Compare two systems
• McGrow, K, Horsman Brennan, A., Preece, J (2004)
  Development of a tool for heuristic evaluation of
  healthcare information systems. (Draft)
  Computers, Informatics, Nursing, Journal of
  Hospice and Palliative Nursing.

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Heuristic Evaluation Exercise
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Tool 2 Cognitive Walkthrough

• Wharton, et al, 1993.
• Evaluates the steps required to carry out a task
• Attempts to uncover mismatches between how a user
  and how a designer thinks about a task.
• You need
• System (actual, simulated, or prototype)
• Task scenario.
• To know who the intended user is

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Cognitive Walkthrough

• Step 0 select task to be performed and list all
  actions to be performed
• For each action
• Step 1 explore system looking for action
• Step 2 select most appropriate action
• Step 3 interpret systems response

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Cognitive walkthrough

• At each step ask
• Does the user know what to do next
• Is there a connection between the correct action
  and what the user is trying to do?
• Will the user know they have made the right (or
  wrong) choice?

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Tool 3 Design Principles

• These principles are at a higher level than
  heuristics
• Affordance
• Visibility
• Feedback
• Simplicity
• Structure
• Consistency
• Tolerance

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Example

• Affords turning, but feedback was poor

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Summary

• Usability of medical devices is significant in
  minimising risk to patients
• Usability has to be designed in its not
  sufficient to say it was human error after the
  fact
• Use simple tools to evaluate usability of medical
  devices and systems.
• The system with the most utility is not
  necessarily the most usable

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However

• In Making Medical devices more User-Friendly,
  Wiklund states Experienced designers of medical
  devices suggest limiting the colour palette of a
  user interface
• However

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However...

• A hospital chain in the US is taping over
  patients' LiveStrong wristbands because they are
  yellow - the same colour as the "do not
  resuscitate" bands it puts on patients who do not
  want to be saved if their heart stops.