Larry, it's been awhile since I've experienced my hypoxia symptoms.  What does one have to do to fly the chamber?

Naf,

 

Ahh, what a great observation.  Our susceptibility to the onset of hypoxia changes with age, weight, body conditioning, fatigue, smoking history, hangover, etc.  Our reactions to the onset of hypoxia can also differ from day to day (Study of employees at 13000 foot scenic lookout in Hawaii).  Another effect is density altitude (and %humidity) - although the percent of O2 per cubic foot remains the same, the are less molecules available in the same volume and at less pressure.  Breathing becomes shallower - Extracted from Mountain High:

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The respiratory volume and rate is determined by the detection of carbon dioxide (CO₂) in the blood, not the lack of oxygen (O₂). CO₂ is principally

generated by spent energy yielding carbohydrates during muscular activity. However, while one is at high altitudes both the CO₂ and O₂ are at lower absolute levels where the lack of CO₂ pressure causes your respiration system to decrease in volume and rate because there is very little CO₂ to purge. This causes you to breathe shallowly at a time you need to breath normally or greater.
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Those flying with a good GPS-guided autopilot, stereo XM radio turned on anything other that Disco music and glass screens are probably close to comatose anyway.  How are you going to remember to consciously breathe deeper?

 

One can go thru the high altitude training chamber to see what happens with sudden depressurization, but I think the main problem is insidious hypoxic impairment at relatively low altitudes, maybe as low as 8000 MSL with density altitudes at maybe 10000 (daytime).  Of course I am old, overweight, out-of-shape and generally fatigued from constantly being grumpy. 

 

The best action is to obtain a digital pulse oximeter and test the readings on the ground (Gee, I start at a lowly 96% O2 saturation). Then, use it while flying at various altitudes, noting that some begin to see impairment below 89% and that 83% or lower is dangerous.  See what readings occur at 10,000 feet before and after breathing is deepened.  These self examinations are much more informative and useful for those that fly unpressurized aircraft generally below 18,000 MSL.

 

These days, my personal decision about O2 is made on the ground.  Why?  Because of the loss of judgement that can take place with mild hypoxia (recognized when I start laughing at my own jokes and I wasn't making any jokes).  So, if the flight is over an hour and at greater than 8000 MSL, the O2 equipment is on and automatically energized at 5000 MSL.  Also, on longer high flights,  this eliminates any O2 deprivation fatigue and mild headaches.  The oximeter is checked from time to time as happiness and joy are felt when the readings are 91% or better.

 

Finally, I have attached 2 word files and 3 pictures of notes taken on a hot summer day (June, 2002) flight from Chicago to Sedona, AZ that resulted in a hypoxic influenced gear up landing.  The first letter is my response for the FAAs 709 ride demand and the second is my analysis of that flight.  Take a peek if you are interested................