Science Question

[kong]

Here is my question: If I’m at high altitude but using my CPAP machine at the time, is the air I breathe through the CPAP basically the same as if I was at ground level? My understanding is that at high altitudes, the proportions of the gases in the air stay roughly the same as at sea level. However, the air is less dense. Does the density change back to normal with CPAP?

[Pugsy]

CPAP has no way to alter incoming air to change it.
All cpap does is hold the airway open so you get whatever air your machine is blowing.
Higher altitude air contains less oxygen than lower altitude air. Using cpap doesn't manufacture oxygen.

[ChicagoGranny]

My understanding is that at high altitudes, the proportions of the gases in the air stay roughly the same as at sea level. However, the air is less dense.

That is correct. Earth's atmosphere is composed of about 78 percent nitrogen, 21 percent oxygen, 0.9 percent argon, and 0.1 percent other gases independent of altitude. This is true even on the peak of Mt. Everest. Among those other gases is CO2 which is so small it is measured in parts per million.

Does the density change back to normal with CPAP?

ResMed machines have been tested effective up to 9500 ft (3000 m). The machines automatically compensate for altitude changes. They may be effective at higher levels, but the testing has not been done.

BTW, some people who move to higher elevations might develop centrals. This could be temporary or longer term.