Travel / CPAP and very high altitude

[BeauPetitNez]

I have a CPAP since 5 years... even if this is cumbersome for travel, I like it veru much and willl never travel without even for one night.
I am 69 and in very very good shape for my age.  My normal pressure set is at 8 and max at 10.

Recently I travel to Peru and Bolivia for 24 days.  The 3th day we travel from Arequipa 2400m to Colca 3250m and have to pass for 2 hours on a part of the Altiplano at 5000m.  I was OK and I did not suffer of the altitude during the trip, only when we had to climb steppy slopes, I was the one that was in the best shape. 
I was using my Resmed each night with confidence because I checked that it was auto-adjusting for altitude.

The point ...  Day after day I was surprized my adaptation to altitude was not improving,  I should ! but never be more adapted to the other 5 of the group.  I my adaptation to altitude was stable, and from the first day to the last ... I was with the same shape !

My explanation... and I would like to have the opinion of the other members. 
I think that with the CPAP adjusting to the same 8-10 pressure ...

EACH NIGHT I WAS RETURNING HOME AT SEA LEVEL ... and in the morning RETURN TO 4000m !!!  WHAT A TRIP EACH NIGHT

I never feeled any discomform, I only realize this because my shape was just stable and dud not improve during the trip.

[silentsnore]

Did you get to chew some of those leafs that locals use over there? 

[Sleeprider]

Did you ever check your AHI for the nights you spent at 4000 meters and compare that to the baseline from home? Your CPAP does not actually provide sea-level pressure, but provides a differential pressure increase regardless of altitude, up to 8000 feet (2500 meters). At 4000 meters, you were well beyond the tested altitude of any CPAP I'm aware of. In any event, you did get an increase of 8 to 10 cm H2O pressure from anyone else. I'd still argue this treated your apnea, but it is your physical condition and ability to adapt to altitude that made the difference compared to others in your group.

[PoolQ]

betting it was oxygen saturation at altitude and not CPAP at night. Check your AHI, if that is good, you can be tested for oxygen saturation at altitude. Just had mine done. 8000ft I was at 88%, 8000ft is the standard pressure for airplane cabins. what fun, O2 concentrator while in flight and insurance will not cover it

[archangle]

Atmospheric pressure is about 1000 cmH2O at sea level. Max CPAP pressure is around 20 cmH2O. It only takes about 500 feet of altitude change to reach that level. The pressure drop at 4000m altitude is about 400 cmH2O.

Your CPAP won't do much about the oxygen level changes due to altitude. A regular CPAP won't help with central apnea.

However, some people do develop central apnea at altitude. The answer isn't completely understood, but it relates to the feedback mechanisms in your respiratory and nervous system.

Also, many CPAP manufacturers specify a max altitude for their machines. I don't have the numbers handy, but I think you're above that altitude. I suspect it's mostly a question of not testing at that altitude or it being less accurate.