Sounds like my husband the last while but add in a little confusion and not really wanting to eat.

I've had blood work done and it came back high,, I have severe COPD

Yes, I also have 3 litres of oxygen while sleeping, there's a tablet I was prescribed also, it's Daliresp,, it also works really well

Stage 3 I think,he uses trelegy,salbutamol,and one other.Also has oxygen

As far as CO2 readings,, it is done by bloodwork