Actually I have high altitude apnea (periodic breathing, Cheyne Stokes), which is why I take a small dose of diamox when I sleep above 11k. The diamox solved that problem beautifully. After a few days, I acclimatize and the apnea goes away. No more diamox needed.
My difficulty sleeping in a tent (at ANY altitude) is not oxygen related (I usually have massive venting --entire walls open). For me, it's probably a combo of just being in different surroundings (different stimuli) and the adrenaline kick of exertion in the mountains. The mind is active, and so sleep elusive.... Relaxation tapes do help me.
