Page 39 - Safety Risk Management for Medical Devices

18 Safety Risk Management for Medical Devices

The event-chain model of causation is one of the most common ways of modeling
accidents. This was depicted in Fig. 3.1. Extending the event-chain model to risk
management, suggests that the most obvious countermeasure for preventing Harm is
to break the chain of events before the Harm happens. While this is a useful model,
care should be taken to consider factors that could indirectly affect the model. For
example, in the 1970s if you wanted to safely stop a car while driving on ice, the
advice was to pump the brake pedal, so as to avoid locking the wheels and skidding.
Modern cars are equipped with antilock brakes. When driving a car with antilock
brakes, the way to stop the car most quickly is to step on the brake pedal as hard as
you can, because the brake system does the pumping automatically. Using the model
of braking from older cars, on a modern car, actually reduces the braking capability of
the car and increases the stopping distance, hence increasing the risk of a car crash.

4.4 RISK PERCEPTION

ISO 14971 [3,7] says “It is well established that the perception of risk often differs
from empirically determined risk estimates. Therefore, the perception of risk from a
wide cross section of stakeholders should be taken into account when deciding what
risk is acceptable. To meet the expectations of public opinion, it might be necessary
to give additional weighting to some risks. In some cases, the only option could be to
consider that identified stakeholder concerns reflect the values of society and that
these concerns have been taken into account.”
Risk perception and tolerance are strongly influenced by human psychology. The
same circumstance would be perceived and tolerated differently by different people. In
fact, this is why stock markets work—some people think that the risk of losing money
is high, so they sell, while others think the risk of losing money is low and they buy.
When an adverse event happens, the public perception of the risk of that event
suddenly jumps up. In the early 1980s Aeroflot, the Russian airlines, had a string of
airplane crashes. All the airplanes involved in the crashes were Tupolev model Tu-
154. At that time, there were people who would refuse to get on their flight if the
brand of aircraft for the flight was Tupolev. We see this in any industry, including the
medical device industry. When a particular medical device is involved in an adverse
event, all other devices of the same type become suspect. You may remember adverse
events related to silicone gel breast-implants ruptures, that terrified many women,
even if nothing happened to them.
Risk perception is also influenced by other factors. For example, whether exposure
to the Hazard seems to be involuntary, avoidable, from a man-made source, due to
negligence, arising from poorly understood causes, or directed at a vulnerable group
within society. People tend to be more tolerant of natural risks than risks due to man-
made sources. Risk to children is less tolerated than risk to adults.