If you're curious about what's involved in an oxygen concentrator, there's an (IMO interesting) overview here https://apps.dtic.mil/dtic/tr/fulltext/u2/a581789.pdf

O2 generators trade dependency on a supply chain to one on power and maintenance.

I find myself wondering about ways to economize O2 use - or does it somehow need to keep flowing even when a patient isn't inhaling? And, given that O2 is being supplemented because of poor absorption, doesn't that mean that their exhaled breath will be high in O2?