Thought I would followup on my own question. Earlier this September I successfully climbed Kilimanjaro in Tanzania. 7 nights. Most nights above 13,000 feet, including one above 16,000. All nights run on batteries, a separate battery for each night. One night the battery ran out before the night did, all others had some charge in the morning. Weird - as in high, real high events per hour - that shrank back to normal when the nightly elevation decreased to usual levels. Tent mate one night said CPAP sounded like it was pushing air / running free flow. Other nights stated sounded normal. Glad to have had the CPAP during the trek; felt like near typical sleep resulted despite the fact i was sleeping in a tent, on the ground, in cold weather, for the first time in more than 50 years. And machine appears to be undamaged from its 7 high elevation nights. Kilimanjaro can be done by CPAP/APAP users - i am proof.