http://www.thebmc.co.uk/world/mm/mm2.htm
A good link to the physiological effects of how to acclimatise to altitudes of the mid 20thousand feet mark. It'f for ground based folk though - the whole issue is acclimatisation. If you dont acclimatise, you wont survive for too long.
As discussed people have successfully climbed Everest without O2, however thier exposure to such extreme altitudes is limited to as short a time as possible.
Yours truly has heard one of UK's finest mountaineers saying that he finds marijuana helps him to acclimatise....and one of Australia;'s best has had a joint on top of Mount Everest....
