That's kind of an unhelpful suggestion from your doc. Is he a pulmonary sleep specialist? Ought to know better. Often there's a gear specialist at sleep centers who knows the ins and outs very well.
If you're talking about condensation in the tube interfering with air flow and perhaps draining onto your face, the term for it is rainout. If you hit cpaptalk.com and search on rainout or rain out, you'll find *plenty* of suggestions.
Here are some that I've tried, or recall reading, in no particular order:
Get or sew a poly fleece tube cover. This is great - I sewed my first, and bought my second for about $15 or $20. It really works for me.
Lower the humidifier level. When I'm camping I turn off the humidifier, because it really pulls juice to heat up the water. I just throw a quarter cup of water in it, which serves as a "pass-over" (unheated) humidifier.
Increase room heat, as suggested above.
In extreme cases, there are heated tube systems. Cpap.com has all that good stuff, if you're willing to spend a little money that health insurance probably won't cover.
The altitude is a secondary issue that does affect the condensation, but condensation is unrelated to the cpap itself - only the humidifier and tube, as I understand it. You do want to search for the specs for your cpap and confirm that the pump is rated to 10,000 feet or whatever. Or, at least I would; I'm very sensitive to getting the full therapy because it does *so* much good for me!
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