[William Tell]

A friend's wife was recently having mental problems. She was diagnosed with a heart problem such that she was only getting about 15% of normal circulation.

Airplanes don't pressurize their cabins at a full one atmosphere. I wonder if a person with an undiagnosed problem like my friend's wife had could become irrational due to the combination of the altitude and the circulation problem.

[ArrogantBustard]

FWIW, I have experienced altitude related hypoxia on an airplane. I became gradually irrational and incapable of concentrating on the task at hand, then blacked out. Teammate observed the problem and assisted in correcting O2 supply failure. Was fully alert in < 5 minutes. YMMV