My first impression was that the photos showed backboards so I had to go look up the difference between a backboard and a stretcher. Sorry for the digression.
Anyway, emergency=stretcher seems to fit the items reasonably well. You may want to look at the suggested additional tags for emergency=defibrillator and see if any of them are also appropriate. They tell things like how accessible they are, if they are indoors, etc.
Probably an Escape chair - Wikipedia. It can also be used for normal transport (e.g. to go down stairs) if the injured person can sit upright, but can’t walk.
I might even hazard a guess that it is this model: Dönges Tragestuhl | Dönges or at least very similar. In any case, it is not really useful as a wheelchair.