M. Frize, Winter 2003

Reliability and Medical Devices

Prof. Monique Frize, P. Eng., O.C.

ELG5123/94.526

February 2003

M. Frize, Winter 2003

Content Definitions and terms (Hardware)

Quality & quality assurance (products)

Software terms and definitions

Approaches to improve quality & safety

M. Frize, Winter 2003

Terms and Definitions

Medical device: Instrument, machine, implant, in vitro reagent, apparatus, contrivance, implement, including part, component or accessory intended for application in diagnosis, or in treatment, cure, mitigation or prevention of disease or intended to affect the structure or any function of the body.

M. Frize, Winter 2003

Terms and Definitions

Reliability: The probability that an item will carry out its function satisfactorily for the stated period when used according to the specified conditions.

M. Frize, Winter 2003

Terms and Definitions

Maintainability: Probability that a failed item will be repaired or restored to its satisfactory operational condition.

Maintenance: Measures appropriate for retaining an item in, or repairing/restoring it to, a stated state, ensuring that physical assets continue to meet their stated missions.

M. Frize, Winter 2003

Terms and Definitions

Risk: The chance, degree of probability of loss, damage, harm, or injury.

M. Frize, Winter 2003

One Definition of QUALITY

Conformance to requirements.

More later…..

M. Frize, Winter 2003

Other Important Definitions

Safety: Conservation of human life and its effectiveness, and the prevention of damage to items as per operational requirements.

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Other Important Definitions

Human error: Failure to carry out a required task (or the performance of a prohibited action) that could result in disruption of scheduled operations or damage to equipment or property.

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Other Important Definitions

Failure: Inability to operate an item within the stated guidelines.

Mean time between failures (MTBF): Exponentially distributed times between failures, the sum of the operating time of given items over the total number of malfunctions or failures.

M. Frize, Winter 2003

Issues on Quality (Control)

Definition: Quality is the totality of features or characteristics of an item that influence its ability to meet requirements of users (or of its intended use).

M. Frize, Winter 2003

Quality Assurance (Control)

Definition: Planned and orderly sequence of all actions appropriate to provide satisfactory confidence that the product conforms to specified technical requirements. (Products)

OR: Bench testing before a product is released and/or distributed to clients. Meet specs? Endurance tests?

M. Frize, Winter 2003

Quality Assurance (Control)

Inspection: Process of examining, measuring, testing, or otherwise making comparisons of the item with the specified requirements.

M. Frize, Winter 2003

Quality Management (products)

Definition: Totality of functions concerned with the evaluation and achievement of quality.

Quality system: Organisational set-up, responsibilities, resources, processes, for implementing quality management.

M. Frize, Winter 2003

Other Concepts (Quality)

Quality measure: Quantitative measure of characteristics and features of an item or service.

Relative quality: Degree of excellence of an item or service.

M. Frize, Winter 2003

Other Concepts (Quality)

Quality policy: Management’s set goals and approach in achieving quality.

Total quality: Business philosophy that involves all individuals for continuously improving an organisation’s performance with respect to quality.

M. Frize, Winter 2003

Other Concepts (Quality)

Quality function deployment: Systematic and structured technique to highlight customer requirements, translate them into a realisable item or service parameters, and guide or direct the process of implementation in a manner that brings about a competitive advantage.

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Software Terms and Definitions Definition: Computer programs, procedures,

rules, and relevant documentation (in contrast to hardware or physical equipment)

Medical device software: Under the US Food, Drug, and Cosmetic Act, any software that satisfies the definition of a medical device is considered a device to which all relevant FDA medical device statutory and regulatory provisions are applicable.

M. Frize, Winter 2003

More Sofware Definitions ...

Software error: Conceptual, syntactic, or clerical discrepancy that results in one or more faults in the software.

Debugging: Process of correcting and isolating errors.

Software testing: This is to determine (through testing) if a program satisfies specified requirements.

M. Frize, Winter 2003

Software Testing Error testing: Ensuring the device

performs correctly in abnormal situations (internal parts failure, power surges or outages, incomprehensible values generated by peripheral devices.

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Software Testing Safety testing: Focus test efforts

on conditions potentially harmful to patient or user.

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Software Testing Functional testing: Direct test

efforts on what the device is supposed to do.

This is the heart of traditional validation and verification procedures…. Exhaustive testing

M. Frize, Winter 2003

Software Testing White-box testing: Employed when

it is required to verify the internal functioning of the device software. This allows the tester to look inside the device and develop tests to discover weak spots in the internal logic of the program.

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Software Testing Free-form testing: Used whenno

formal test plan can find each important software bug. This test subjects the device to additional stress on top of the formal approaches listed previously.

Test the device in unconventional and unexpected ways to attempt to provoke a failure.

M. Frize, Winter 2003

More Sofware Definitions ...Software quality: Totality of

characteristics and features of a software item that determines its capability to meet specified requirements or conform to specifications.

Software reliability: Probability a given software will operate for a specified time interval, without an error, when used within the framework or designed conditions stated.

M. Frize, Winter 2003

Comparisons (hardware VS software)

Hardware Software

parts degrade no degradation parts

processes governed physics not physics failure modes different interfaces physical interfaces

conceptualfewer paths (cause failures) more distinct

pathsless sensitive to small errors very sensitive

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Error Prevention Observing workers and performing

audits after incidents or accidents (OR)

Train and educate Try to design devices fool-proof Labels and warnings may help Guards or special lock mechanisms,

etc...

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Main Source

Medical Device Reliability and Associated Areas. B.S. Dhillon,CRC Press, 2000.