Earlier quoted context omitted.
I know nothing about medicine, but is there any way to skip the lungs and give patients oxygenated red blood cells directly?
Yes: https://en.wikipedia.org/wiki/Extracorporeal_membrane_oxygen...
Human bodies are just too damn complex. Even when the problem is clearly identified--a lack of oxygen in the blood--there's no way to just insert more that doesn't cause a hundred new problems :-/ Natural selection seems to be really bad at modular design.