FAA High Altitude Chamber – Hypoxia

As many of you may know I’m a private pilot – it was a childhood dream for me to learn to fly and I count getting my pilot’s license among my greatest life experiences.

A huge part of being a pilot is training. In order to get a pilot’s license you have to train again and again on procedures until you can recite emergency checklists, and perform stalls in your sleep. Once you have your license, the training doesn’t stop. You have currency training requirements every 90 days and have to pass a check ride with an instructor every two years.

In addition, we are constantly training to help increase the odds that if something goes wrong, we’ll have the knowledge and skills needed to deal with it. Having personally experienced an engine failure while flying and being forced to make an emergency landing (ask me about it sometime), I know that this constant training philosophy saves lives. We train for instrument failures, we train for engine failures, and we even train for ourselves failing.

Last Friday, as part of this on-going training, I had the opportunity to “fly” in the FAA’s PROTE (Portable Reduced Oxygen Training Enclosure). This chamber allows the instructors to simulate the effects of “hypoxia”, that is, reduced oxygen encountered at 25,000 feet so pilots can learn how to recognize the symptoms of hypoxia and how to respond properly. The FAA Civil Aeromedical Institute travels around the country with the chamber, educating pilots in order to improve safety. Due to the hard work of David Waggoner and his team at Willamette Aviation Service, LLC at the Aurora airport, many local pilots got the rare opportunity to experience hypoxia in a safe environment.
What is Hypoxia?

Our atmosphere is about 21% oxygen, and 78% nitrogen. As we gain altitude the composition stays the same, but the partial pressure of oxygen reduces. What this means is that there is still about 21% oxygen, but there’s less of it overall. In addition, our bodies become less adept as extracting and using it. Hypoxia occurs when there isn’t sufficient oxygen in the blood, tissues, and/or cells to maintain normal physiological function. As a result, certain functions begin to shut down; if hypoxia is not corrected quickly, it can lead to death.

The effects of hypoxia are varied by individual, but generally your cognitive function greatly diminishes and you become euphoric and unable to accomplish simple tasks or follow basic instructions. The effect is very much like being drunk, and perhaps most concerning is that the euphoric feeling doesn’t make you too worried about the fact you can no longer fly the airplane. Several accidents have occurred as a result of this and that is why the FAA requires that if you fly above 12,500 feet for more than 30 minutes, supplemental oxygen must be used by the flight crew. However even if you fly lower than 12,500 feet you can still be at risk.

Hypoxia chart

[Image from http://www.code7700.com/slow_onset_hypoxia.html]

My Experience in the Chamber
My hypoxia day started with a 90 minute classroom training on the nature of hypoxia and its effects. Then it was off to the chamber. Before entering the chamber, they give you a sheet of paper with lists of symptoms to check off as you get them. They told us again and again that as soon as we had three symptoms, we were to put our oxygen masks on. They made us repeat this instruction prior to entering so many times it was laughable – I didn’t get the joke until later.

I then entered the chamber with a group of four other pilots and one FAA instructor who was there to provide assistance if anyone needed it (he stayed on oxygen the whole time). We all took our seats and began writing down our heart rate and blood oxygen levels every minute (so that we could document our own decline). Initially I felt fine, then within a minute I felt a bit light headed. Another minute went by and I enjoyed watching how my fellow pilots started getting silly. I dutifully marked off symptoms as they came. Tingling in my cheeks, check. Lightheadedness, check. Dizziness, check. By this point I was about 4 minutes in, I had my three symptoms. I had also lost all interest in my paperwork – no more entries were made by me. I enjoyed looking at the other pilots and how silly they were, and only kind of noticed the instructor was talking to me. When he finally dragged my attention away from the pilot next to me (who was already back on oxygen) he asked me to do some simple math problems. Which I attempted. When he finally had me put my oxygen mask on, I initially felt cheated. I felt like I hadn’t gotten “real” symptoms and that I missed out.

It wasn’t until the debriefing afterward that I noticed I had disregarded the three-symptom instruction (which had been beat into me moments before), and that I had in-fact been quite impaired. I couldn’t recall exactly what math he had asked me to do. I had stopped doing my worksheet because I lost interest in it and time had also appeared to pass extremely quickly.

It was a sobering thought (once I was back at sea level) that not only had I been very impaired, but I failed to recognize it in myself at the time, and I had no desire to do anything to correct the situation. This is the problem with hypoxia – you don’t think you have a problem, and feel no urgency to fix it. In fact, it was actually a quite enjoyable experience.

Now that I know how the early symptoms manifest themselves in me, I hope if this ever happens I’ll recognize it and descend (or put my oxygen mask on) before I get too loopy to fix it.

There are a number of videos all over the internet of hypoxic pilots acting silly. Worth a laugh if you have a couple of minutes to kill.

Dave Van Dyke



“4 of Spades” Video of a pilot in a training situation as he develops symptoms of hypoxia over the course of less than 1 minute.