Page 37 - Safety Risk Management for Medical Devices

16 Safety Risk Management for Medical Devices

intended use by the manufacturer, generally understood patterns of usage can construe
the intended use.
Safety is an emergent system property. That is because users interact with the
system, not with just parts of the system. For example, a car is a system. Users interact
with a car-system for the benefit of transportation. A tire is a component of the car-
system. A tire disintegration does not pose a safety risk, if it is sitting in storage. But a
tire disintegration does pose a safety risk if it is part of the car-system.

4.1 RISK DEFINITIONS

There are a number of definitions for “risk.” Let’s examine some:

1. Combination of the probability of occurrence of Harm & the severity of that
Harm [3,7]
2. The objectified uncertainty regarding the occurrence of an undesirable event
[11]
3. The probability of occurrence of something undesirable
4. Probability of sustaining Harm in a Hazardous Situation
To provide beneficial information, risk needs to be measurable—quantitatively or
qualitatively. Simply knowing there is a risk of Harm is not very useful. One needs to
know the magnitude of risk to be able to make a sound decision. Consider disclosure
of risk by pharmaceuticals. Pfizer describes the following risks for taking Lipitor, a
common statin drug for fighting cholesterol:

• Diarrhea
• Upset stomach
• Muscle and joint pain
• Feel tired or weak
• Loss of appetite
• Upper belly pain
• Dark, amber-colored urine
• Yellowing of your skin or the whites of your eyes, etc.

There is no citation of the probability of occurrence for any of the above harms.
Without that information, it is not possible to make a sound decision as to whether to
take Lipitor or not. Consider if the probability of occurrence of a Harm were 99%
versus 0.01%; wouldn’t your decision be affected by that knowledge?
If quantitative data is not available, relative, qualitative information would also be
helpful. For example, if Crestor, which is another popular statin drug claimed that
relative to Lipitor their risks of side-effects are lower, a patient might choose Crestor over
Lipitor.