There have been a lot of good posts on this subject recently - enough information to make anyone think twice about the effects of hypoxia. I think there has been one important factor that has not been mentioned, and that is the time a person has to aclimitize to the higher elevations. Anyone who has spent time in the mountains knows that the body can function very well at high altitude.  I have spent many days at elevations in excess of 15,000 feet, several times over 17,000 feet, including a climb to an 18,300 foot peak. The only effect I felt at the time was very rapid heart and respiration rates during the last several hundred feet of the climb. Also often experienced waking at night gasping for breath (Cheyne-Stokes breathing?). However, there were no lasting effects to report, except possibly the loss of a couple IQ points -- perhaps that's how I got involved in building one of these airplanes!!??!!
   The point of this rambling is that I spent a week or more getting to those high elevations while you who climb into your high performance airplanes can get there in a matter of minutes.
                           Charles


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