LOL!
Above 13,000 ft, Oxygen required......................lest you get Hypoxia
Above 14,000 ft, temperatures are sub-zero............Hypothermia pap.
Above 18,000 ft, you should be in a pressurized cabin....Otherwise you develop Decompression Sickness & your blood bubbles up like foam.
By 36,000 ft, you're long dead. .....with limited traces of Oxygen in the body, frozen at -57 deg celcius, with bubbles in the veins & tissue.
TULIA.........UFUNZWE!