I finally got to do something that I’ve wanted to do for a long time…fly the altitude chamber. My pilot class in the US Army flight training did not get to do the training, and I’ve been interested ever since. So, when the MMSTF scheduled an altitude chamber class around a MMSTF weekend seminar at OKC, I knew I wanted to be a part of it. There were about 15 of us in the class (all PA-46 drivers) and we had a super time. Here’s my perspective…
We went through entirely too much security in order to get onto the Mike Monroney Aeronautical Center at OKC, but finally got to the building where the Altitude Chamber is located. The entire morning was spent going through professional academic classes about hypoxia administered by incredibly professional instructors. They covered much of the physiological aspects of a hypoxia while not being boring at all. My kudos go to the FAA instructors…
We entered the altitude chamber and sat down on each side of the chamber in airline-style seating in front of a console that gave access to an oxygen mask and all associated controls. We then listened to the instructor via earphones. They started the chamber altitude up to 6,000ft and then brought us back to OKC elevation fairly quickly, mainly to make sure no one had any physiological problems that would preclude them from continuing with the rapid pressure changes that were coming soon. Then, we sucked pure O2 for about 20 minutes while watching a video about Situational Awareness (SA). Once everyone was ready, the fun began.
They simulated a rapid decompression by dramatically increasing the altitude to 18,000ft. A fog was created by the rapid decrease and everyone donned their masks. They then (more slowly) brought the chamber altitude up to 25,000ft while we had masks on. With the oxygen mask on, the biggest physiological perception I had was an incredibly bloated stomach. I must have had some gas which was expanding. I belched a few times and farted more than once, but the bloated feeling did not go away until much later in the event.
The people on my side of the chamber were instructed to take our masks off first. I had a pulse-oximeter on my finger and at the start of the exercise and it told me that I had 100% O2 saturation with a pulse of 50 bpm. At one minute into the test I was at 73% O2 with 66bpm. At two minutes into the test, I was at 67% O2 saturation with 58bpm. For the rest of the 5 minutes at altitude I did not have enough mental capacity to remember to write the numbers down. After 3 minutes I have spotty memories and remember seeing the low 60’s on the O2 saturation, being asked a few questions, feeling somewhat weird in my body, but my mind was definitely not putting full frames of memory together. The video of me while hypoxic does not show much, in fact I was answering questions, holding up fingers, and responding apparently normally, but I can assure you I was not normal. I never lost consiousness, but had trouble organizing my thoughts. It was as if time had slowed down tremendously. At 5 minutes into the test, I was told to put back on my mask and did. Within 10 seconds I had an O2 saturation of 99% and felt just fine, except for the bloated stomach.
The biggest lesson I learned form this is that my body does not have a huge response to hypoxia, meaning I don’t get a huge headache. hot/cold flashes, or other responses. My body feels somewhat queasy and I have an unusual feeling that I simply call “fatigue”, but that is a poor descriptor of this feeling. This is really bad news since the point of the whole chamber experience is designed to determine each person’s most immediate physiological response to hypoxia so we can recognize it in the real world and respond appropriately. Since I have slight symptoms, I really need to be careful to recognize those symptoms early so I don’t get myself into a situation where I “fall asleep” while hypoxic and don’t respond in a manner to appropriately get out of the situation. I saw several of the others in the chamber start to “go to sleep” fairly quickly after being nearly alert just a few minutes beforehand.
I came away from the experience knowing that I have about 3 minutes of useful metal capacity where I could probably respond to an emergency at 25,000ft with no trouble, but if I don’t do the right thing quickly, I could very easily do the wrong thing (or nothing, which is the wrong thing) if I didn’t start down fast from an emergency rapid decompression. I thought there would be a correlation between physical conditioning and ability to handle the lack of partial pressure, but I could not make that determination from this experience. A couple people were younger than me and a few older, but the ability to perform with less pressure didn’t seem to follow any of my preconceived notions. I work out fairly regularly, especially my cardio-vasular system, so i thought I’d have few signs. This was just not the case. My reasonably good physical condition doesn’t preclude me from falling off the same cliff mentally as everyone else. I saw a few people faint or mildly pass out, but I also saw some older people seem to be unaffected by the lack of pressure. As I fly airplanes that go higher, I really need to be in a position to get down quickly in case a rapid decompression occurs. I came away with the knowledge that I too am susceptible to hypoxia, and I need to respond to an emergency in case one present itself.
This was excellent training, and everyone who flies high-altitude should look for the day when they can participate. The FAA offers it for free…you just have to sign up and dedicate a day to the training. I highly recommend you do.