chapter 16 medical device reliability. 16.1 facts and figures, government control and liability nfpa...
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Chapter 16 Medical device reliability
16.1 Facts and figures, government control and liability
NFPA 1200 deaths per year due to faulty instrumentation
Operator error account for well over 50% of all technical medical equipment problem.
4%-6% of hospital products were sufficient dangerous to warrant immediate correction.
16.2 Medical electronic equipment classification
• Category A-equipment requiring high reliability because it is directly and immediately responsible for the patient’s life or which may become so in emergencies.
• Category B-used for routine or semi-emergency, there is time to repair.
• Category C-not essential to a patient’s life or welfare but serves as a convenience equipment.
16.3 medical device recalls
The recalls were classified into 9 problem:• Faulty product design• Contamination• Mislabeling• Defects in material selection and manufacturing• Defective components• Miss assembly of parts• Electrical problem• Radiation violations• No pre-market approval and failure to comply with GMPs
%70
16.4 Medical device design quality assurance
FDA preproduction or design quality assurance program is composed of 12 elements:
1. Organization2. Specification3. Design review4. Reliability assessment5. Parts/material quality control6. Software quality control7. Design transfer8. Labeling9. Certification10. Test instrumentation11. Manpower12. Quality monitoring subsequent to the design phase
16.4.1 Organization
Preproduction quality assurance program (PQA)
16.4.2 Specification
Performance characteristics, such as reliability, safety, stability and precision
16.4.3 Design Review
FMECA
FTA (fault tree analysis
16.4.4 Reliability assessment
Parts reliability, subsystem reliability and system reliability
16.4.5 Parts/material quality control
Develop a preferred P/M list
16.4.6 Software quality control
SQPA
16.4.7 Design transferTransfer to scale up production
16.4.8 Labeling
16.4.9 certification• Overall adequacy of quality assurance plan.• Resolution of any discrepancy between the
standard/procedures employed to construct the design during the research and development phase and those identified for the production phase.
• Adequacy of specifications.• Suitability of test approaches employed for evaluating
compliance with the approved specifications.• Adequacy of specification change control program.• Resolution of any discrepancy between the approved
specifications for the device and the end product device.
16.4.10 test instrumentation
16.4.11 ManpowerEnough qualified person to perform the design activity
16.4.12 Quality monitoring subsequent to the design phase• Identifying trends or patterns associated with device
failures.• Performing analysis of quality related problem.• Initiating appropriate corrective measures to stop
recurrence of the above failures or problems.• Reporting in a timely manner the problems found either
in-house or in the filed use.
16.5 Human error occurrence and related human factors
16.5.1 Control/Display related human factors guidelines• Controls, displays and workstation are designed considering user
capability.• Switches and control knobs correspond to medical standard• Design facets are consistent with user expectation.• Control and display arrangements is well organized and uncluttered.• Tactile feedback is provided by control• Knob ,switches, keys are arranged and designed to prevent any
inadvertent activation.• Color and shape coding is easy to identification.• Intensity and pitch of auditory signals easy to be heard.• Visual signal’s brightness is easy to be perceived.• Items should consistent between display and instructional manual.
16.5.2 Medical device maintainability related human factor problems
16.5.3 Human factor pointers for already being used/to be purchased medical devices
Information come from1. Complains2. Observation3. Installation problems4. incidents
16.6 Medical device software
16.6.1 Software testing for improving medical device safety
Manual software testing
Free form testing
White-box testing
Functional testing
safety testing
Approaches to manual software testing
Error testing
Automated software testing
Four purposes:
1. To stimulate the test target
2. Monitor associated response from the device
3. Record the end results or conclusions
4. Control the total process.
16.6.2 Quadriplegias delivery system software reliability program core elements and software safety improvement with redundancy
16.7 Source for adverse medical device reportable events and failure investigation documentation
1. Service/repair reports2. User/distributor records3. Published/unpublished literature sources4. The manufacturer’s product complaint-handling
mechanism5. In house research/testing evaluation/etc. records6. Legal records7. Sales representative contact.8. Technical service customer contacts.
16.8 A small instrument manufacturer’s approach to
produce reliable and safe medical devices
1. Analyze existing medical problems2. Develop a product concept to find a solution to a specific device is
operating3. Evaluate environments under which the medical device is
operating.4. Evaluate the people expected to operate the product under
consideration5. Building a prototype6. Test the prototype under library environment.7. Test the prototype under the field operating environment.8. Make changes to the device design as appropriate to satisfy the
actual field requirement.
16.9 Aerospace and medical equipment reliability and reliability approach comparison