Page 97 - Safety Risk Management for Medical Devices

76 Safety Risk Management for Medical Devices

SW doesn’t
sense VF

Stuck discharge VF Not
switch detected
Sensing signal
path disrupted
Disrupted
Separated delivery path No therapy
connector

Shock Cap low
Pads not on charge
plugged in
Energy
unavilable
Battery
defective
Power supply
failed
Aftermarket
Charging circuit battery; low
failure capacity

Battery old
and low
Figure 12.4 Example of Mind Map.

An advantage of Mind Map over FTA is that it is simpler to learn than FTA and
software for Mind Mapping is either free, or very low cost.

12.2.2 Theory
Starting from a central theme, which is marked as the central node, second layer
nodes are connected to the central node. The second layer nodes comprise all the
immediate, necessary, and sufficient pathways to the central node. This pattern repeats
for each second layer node, and further nodes successively.
In the absence of FTA’s specialized nodes such as Normal Event, and
Undeveloped Event, develop each branch to the degree that it makes sense. If an
event is undeveloped due to the current lack of information, you can put a TBD in
there as a reminder to come back to it.
The main purpose for constructing a Mind Map is to graphically tell the story of
how an undesired event can happen. This information will later be captured in the
Sequence of Events in the PHA.