Everybody keeps saying that
FMEA is a purely bottom-up methodology but the VDA/AIAG guideline on FMEA explains how it can be used on complex systems in a top-down way as well (since 1996!). You start with your system structure, identify the necessary functions of each element in that system, then the failure modes and finally the causes/effects and the evaluation. Creating FMEAs this way is maybe more difficult than a bottom-up brainstorming approach but prevents you from forgetting systemic part interactions that are not necessarily self-explanatory or easy to spot.
We use a 14971 risk analysis approach that includes user errors and forseeable device failures to generate requirements for our devices. Then, after the technical requirements have been defined, we use such a systematic FMEA to discover what could lead to the device not performing as intended. This helps us to identify and document design outputs essential for safe use, create a quality control strategy and even develop safe production processes.
We inherit the severity in that device
DFMEA from our high level risk analysis (i.e. if a component failure could lead to a patient risk, its severity is identical to the respective severity within our 14971 risk analysis)