Did you ever try wearing a pulseox and seeing what your sat looked like? As long as sats aren't ever dipping below (NOT medical advice, but I'm being conservative here), say, 90%, brain damage is very remote. Plenty of COPD patients walking around with sats in the 80s, or even 70s.

But as someone with bad lungs...yeah, you only get one set and most meds/treatments are partial symptom relief at best.