Increased lung capacity?

Higher altitude affects red blood cells and hemoglobin. There is less atmospheric oxygen at higher altitudes. "Altitude sickness", weakness, short of breath. Body needs some time to adapt. For some only a few days, for others a bit longer. Exercise (skiing, hiking, fast walking) can seem more laborious.

You may want to supplement with magnesium... most apnea sufferers pre treatment had a sever magnesium shortage because the condition causes you to use it up. A lot of things improved for me after supplementation.

as for lung capacity and breathing, I seem to be better than many now, I'm 280 and quite overweight (down from 306) but at my work's gym I easily beat this guy who wanted to compete with me while on the elliptical .

what is may happening is that you can achieve better control of asthma when you use a cpap and have sleep apnea control

I'm having to run to the ER and get solumedrol for rib pain and came down with pneumonia, having bad inflammation these days and the inhalers stopped working. I take singulair and am too weak to use the nebulizer. maybe I could restart spiriva but that may cause glaucoma which I have

I was really handicapped by antibiotics I think.

XPAP therapy does not inflate or push air into your lungs. It simply splints open the airway so you don't stop breathing. XPAP is very low pressure .3 PSI and high volume, similar to being in front of a fan. Stick a balloon over the output of your machine and see how the balloon does not blow up just like your lungs don't . I don't see how it would expand your lungs.

There are a lot of reasons you can get short of breath on exertion, and some of those reasons have nothing to do with your lungs. There are people with severe COPD who run marathons.

There is also some correlation that pot smoking increases lung capacity. I guess anything is possible.