Hey Annie: An mg specialist around here? Ha! Not likely!!!

He is a neurologist, but he's always only done sleep stuff.
Your plane oxymetry levels sound scary to me!!! Here's what I know, mostly from this article in the New England Journal of Medicine, which looks pretty solid from a statistical analysis point of view, which is all I'm good for:
http://content.nejm.org/cgi/content/full/357/1/18
(I hope that worked!)
The short story is that absolutely you're right - oxygen saturations fall. After five hours at 7000 feet cabin pressure (most modern airplanes) the saturation levels fall to a little above 94 with the lowest person at 90. They did have one person out of 502, a 75 year old woman, whose saturation level fell to 78 after 5 hours at 8000 ft and they pulled her right out of the study immediately. They also had half of the participants exercising on a treadmill for 10 minutes, and the average sat level fell to about 94 at 7000 ft.(by the way, I can't even IMAGINE getting on a treadmill at that point-yikes).
I have an oximeter that records the data and I used it this weekend and it looks like I was bouncing around between 78 and 90. Mostly a lot of ink filling in the '80's. I do feel like I'm suffocating, so I wasn't surprised.
As for the breathing machine, I'll definitely get it and use it. My concern is that the one my doctor wants me to get *doesn't* give me a break, it's going to make me breathe out against pressure, which makes me feel exhausted and out-of-breath just thinking about it. I would love to have a bipap instead but I don't know how to fight for it. I'm going to work on it though.
Anyway, thanks so much for the input, you're full of knowledge as usual!!