My AHI (clear apnea and hypopneas went up - obstructive stayed constant) and especially "periodic breathing" both went up multiple-fold (5-7x) on the first night at a higher altitude and then slowly decreased until moving up in altitude again. I would have loved to stay and continue the experiment longer to see where my AHI would level off at high altitude (vs. near sealevel where I live), but my vacation ended.
Upon returning, by the second night, I was exactly back to "normal".
I was definitely above the altitude rating of the DreamStation and didn't change any settings. The machine ran OK, with no errors or notices (other than surprisingly high AHI and periodic breathing). What does the machine actually do to compensate for altitude? I thought the machine only measured the difference in pressure between inside of the mask and outside of the mask (not absolute pressure above sea level). The blower probably has to work harder to pressurize the thinner air, but not sure what would be different at intermediate pressures?
Any high altitude living people comment if they achieve an AHI <=5 and what their periodic breathing percentage number is???