The end user for me is the company for whom i have designed the product, and the end user for the company are doctors.
In that case why do you not write what I call an "end user manual template". This is what I give to the tech writers when such are involved. This will give someone at "the company for whom i have designed the product" the opportunity to write a manual in "MD language" and ask you what s(he) does not understand in your template.

Re the manual for the hardware: I just got a quote for some cheap switching power supplies and the quote stated "high reliability with an MTBF of 2.6 Million hours". For medical equipment you should do better and, in that case, it is cheaper to produce a couple of spare boards than trying to fix the possible ONE defective showing up every 10 years cause nobody will have any idea how to approach fixing it.

Erik