Page 131 - Safety Risk Management for Medical Devices

110 Safety Risk Management for Medical Devices

The UMFMEA is a System-level FMEA, similar to System DFMEA or System
PFMEA. This is because the User interacts with the whole System. Therefore the
scope of analysis of the UMFMEA is the entire System, and End Effects of the
UMFMEA can be System Hazards. The input to the UMFMEA is the set of System
use scenarios, tasks, and step actions.
Just as in other FMEAs, the UMFMEA discovers many Failure Modes, only some
of which may have a safety impact. Knowledge of the nonsafety-related Failure
Modes is useful in improvement of the design for better user experience or product
effectiveness. Risk management leverages only the Failure Modes that have a safety
impact. The UMFMEA is an analytical tool that serves both the risk management and
the usability engineering efforts.
Normally the UMFMEA considers the ways in which every task in the normal flow
of events could go wrong. But users don’t always follow the normal flow. Sometimes
the users make mistakes and go down unexpected alternate paths. They may even
improvise and create new pathways. Due to the fact that the number of alternate paths
may be very large, it may be that task analysis doesn’t consider all the possible alternate
paths. It’s advisable to try to consider the alternate paths that are related to safety criti-
cal operations of the device.
UMFMEA does not consider malice in the scope of analysis.

12.8.1 Distinctions
There are many special terms used in the domain of usability engineering and
UMFMEA. It is important to have a clear understanding of these terms and their distinc-
tions. Without this clarity, it would not be possible to properly analyze the medical
device, or communicate your analysis. Below some of the important terms are examined.
Use: Using the device for what it was intended and per the supplied labeling.

The outcomes from attempted use can be:
• Successful use
• Failed use
1. Step action is not performed.
The user has the intention to perform action but is unable to complete the
action.
Example: UI does not permit the performance of the action, or UI is so
confusing that the user cannot perform the action.
2. Step action is performed, but with difficulty.
The user has the intention, and executes the action but with difficulty.
Example: Complicated UI causes the user to make mistakes that he/she
recognizes and corrects the mistake. The action is ultimately completed but
with struggle and errors.