FAA's PROTE Chamber Simulates Symptoms of Hypoxia Very Well

5:02 PM


By Dan Pimentel 

Airplanista Blog Editor

All general aviation pilots have heard the term "hypoxia" and know what it is. You become "hypoxic" when the air you are breathing does not contain enough oxygen to remain conscious and maintain critical cognitive functionality. To fly in pressurized airplanes up in the flight levels, you need to be fully trained on how to recognize when you are becoming hypoxic. But most GA pilots who fly well below FL180 have never experienced what becoming hypoxic feels like. That was me until this weekend.

I have just completed FAA's Hypoxia Training Course in the FAA's Portable Reduced Oxygen Training Enclosure (PROTE) with fellow EAA chapter 1457 member Larry Lowenkron. This traveling altitude "chamber" is capable of producing hypoxic environments at ground level by altering the fraction of ambient oxygen, thus avoiding some of the risk factors associated with altitude chamber training. It's a pretty cool portable system, using microprocessors that monitors two oxygen sensors, a carbon dioxide sensor, and an atmospheric pressure sensor to calculate the simulated altitude and, in turn, to control nitrogen-concentrating air units, CO2 scrubbers, and vents (as needed) to maintain the enclosure at the desired simulated altitude setting.

After a morning presentation by FAA staff on just what hypoxia is and why it can incapacitate a pilot, we were led into the Civil Air Patrol's offices at Aurora (OR) State Airport (KUAO) where the PROTE had been set up. At a short briefing, we were told that this would be a five-minute simulation at 25,000'. In our hands were clipboards with a sheet containing a variety of math problems, a maze diagram, and a series of five boxes (one for each minute we'd be in the chamber) with symptoms of hypoxia. We were also fitted with a pulse oximeter on our finger, and wrote down our baseline readings...mine was 98% O2 and a pulse of 60 bpm.

As our briefing took place, we watched the previous five pilots in the chamber, and it looked pretty tame. No gagging or passing out, nobody screaming to be let out...a perfectly harmless environment, or so it seemed looking in from outside.

When it was our turn to enter the PROTE, we took our places in our five numbered chairs, and instantly, I sensed an odd smell in the "scrubbed" air. During the first minute, I felt in total control but a wee bit "woozy," and could easily check off three of the hypoxia symptoms I was feeling, air hunger (a sense of suffocation), dizziness and fatigue. So far, so good... 


But as the second minute came and went, I could feel a distinct and odd feeling, similar to euphoria, but not a "high" feeling. It was more of sort of looking around, being aware of the situation, and feeling a bit helpless to do much about it. That all changed in the third minute when my oximeter displayed in the 60% range. The instructor in the chamber looked me square in the eyes and asked me to count backwards from 100, by threes. He was right next to me, and I just stared at him, speechless, until he asked again. It took maybe 30 seconds for my brain to engage and I struggled to say "97" followed a few seconds later by "94." But that was as far as I could go, and muttered some gibberish like "84" next...it was obvious I was not thinking clearly. In the fourth minute, I tried to sign my name to the sheet on the clipboard before me, and all I could do was scribble. My oximeter was down in the high 50s now, and I tried to do the crossword puzzle on the sheet...completely impossible. I was incapable of even understanding up from down. At this point, they had me put the oxygen mask on and take three deep breaths, and my oximeter rebounded almost immediately into the 70s and 80s. Soon the session was over, and while my oximeter read in the 90s again, I struggled to find the mental power to set the oxygen mask on the chair and wipe it down with a provided alcohol towelette.


In debriefing, I still felt sort of "loopy"...and as I write this 24 hours later, I still would not feel comfortable flying as PIC. The whole session made me feel "off" and took a physical toll on my body, sapping nearly all the energy I have even a full day later.

But this training was incredibly valuable to me in that it taught just how dangerous hypoxia can be. This was FIVE MINUTES at 25,000', and there was no way I could have flown anything, or even responded to ATC radio calls. I was pretty much worthless at three minutes, and had it gone to seven minutes, I surely would have passed out from oxygen deprivation.

Of course, most of GA pilots out chasing hamburgers will never be up at FL250 when the oxygen system craps out. But what this training teaches is that when FAA says the pilot needs to use oxygen above 12,500', and all occupants need to use it above 14,000'...they mean it. The reason is that hypoxia does not slap you upside the head rendering you a flying vegetable, it instead creeps up on you, and incapacitates you slowly, so you probably do not even know it's happening before it is too late to do anything about it.

There have been times I have flown for long distances at 10,500' in my Cherokee, and did not remember any adverse effects of hypoxia. But that's the inherent danger of hypoxia...you may not even know it's effecting you. That missed radio call, or a struggle to hold altitude? Yep, could be early onset hypoxia if you are up high for a long time. You might not get completely stupid like we did in the PROTE chamber, but I believe any of us can certainly diminish out flying skills in that situation, up high at cruise for a long time, fat, dumb and happy.

I recommend this FAA hypoxia training for all pilots...it should be part of the private pilot syllabus. It teaches you to be aware of the very first signs so you can react quickly. And if you fly up in the flight levels and have not taken this type of hypoxia training from FAA, do it tomorrow, it could save your life.

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