Aviation medicine. Problems of altitude I: hypoxia and hyperventilation.

Even modern aircraft still expose their passengers to some risks from lowered atmospheric pressure."' Concorde commonly cruises at altitudes of 50 000-60 000 ft (15 240-18 288 m) where, if unprotected, its occupants would be unconscious within 15 seconds and dead four to six minutes later from lack of oxygen.2 Even at the more usual cruising altitudes of commercial aircraft-30 000-40 000 ft (9144-12 192 m)- unprotected passengers and crew would rapidly succumb. Of course this does not happen, thanks to the protection of the aircraft pressure cabin. The well being of the air traveller within this artificial environment is, however, always threatened by the problems of altitude extending beyond lack of oxygen to decompression sickness, cold, and simple pressure effects.