Page 132 - Safety Risk Management for Medical Devices

Risk Analysis Techniques 111

3. Step action is performed incorrectly.
The user has the intention and completes the task, but incorrectly. To
analyze this outcome let’s refer to Fig. 8.2. To isolate use-failures from
design-failures, we’ll focus on the right side of the picture. The potential
causes of performing a step action incorrectly are:
a. Incorrect perception—The User doesn’t see/hear/feel the stimuli that is
expected to be perceived, and therefore performs the action incorrectly.
b. Incorrect cognition—The user has a wrong mental model of the system,
and with the correct perception, performs the wrong action. Possible
causes: lack of knowledge/training, unfamiliarity with the device. Or,
user has a memory lapse. That is, the user knows what to do, but for-
gets, or makes a mistake.
c. Incorrect action—The user has the correct perception, cognition, and
intention but fails to perform the action correctly, e.g., a slip of the fin-
ger, or physical inability to reach/pull/twist/etc.

Failed use can be both due to action, or lack of action by the User. An unexpected
outcome either in the patient physiology or in the medical device is not considered a
Use Failure. Use the above three types of Failed-Use categories to guide in the dis-
tinction of Use Failure from other types of failures.
Abnormal use: Use of the device in a manner that goes beyond the Risk Controls
which are put in place by the manufacturer. For example, alteration of a device, disre-
gard of device alarms, or use of the device under conditions that are clearly prohibited
by the manufacturer.

Example 1: Ventilator alarm system is intentionally disconnected, preventing
detection of Hazardous Situation (Source: IEC 62366 [14], sec. C.3).
Example 2: Contrary to the indications in the accompanying documentation, a medi-
cal device is not sterilized prior to implantation (Source: IEC 62366 [14], sec. C.3).

Misuse: Incorrect or improper use of the medical device (Source: ISO 14971
[3,7]— unofficial definition).
Reasonably Foreseeable Misuse: Misuse is not use failure. It is deliberate and well
intentioned. Abnormal or Misuse of the device that is pervasive and well known is
Reasonably Foreseeable Misuse. Typically, off-label use of a medical device/drug for
the benefit of patients is seen is foreseeable misuse.
Example: It has become routine to send patients home with intravenous (IV) infu-
sion pumps. These pumps were originally designed for use in hospitals by trained
medical professionals.

Malice: Use of a device with the intention to harm the patient or damage the device.