Originally Posted by
JDiver
Equivalent available oxygen at 30,000 msl is 6.3%, as opposed to 20.9% at sea level. Anything under 19% isn’t good for human survival. Pretty amazing - and pretty desperate.
True yes the low oxygen levels are worrisome, but benefiting them is the cold temperatures associated with higher altitudes. Cold slows the metabolic rate of the body and thus the demand for oxygen by your cells, lengthening the time they can go without suffering irreparable damage. There's a saying in medicine that you aren't dead until you're warm and dead for precisely this reason, and this also explains why people with prolonged cold water drownings can still end up surviving. Stowing away in a non-pressurized portion of the aircraft is very similar physiologically to a cold water drowning: hypoxia + cold.