OK I lied, it was not that bad– or was it– read and you decide.
Periodically as aircrew members we were required to undergo training in the altitude chamber. It was not something that any crewmember relished. The goal was to ensure that we fully recognized the symptoms of oxygen deprivation or hypoxia. This could only be done in a hypobaric chamber which could simulate conditions that a crewmember could experience at high altitude. The chamber from the outside looked innocent enough. It was enclosed in a small room with a viewing window, equipped with powerful pumps to remove the oxygen and simulate low air pressure.
Once in the chamber, we learned what our symptoms would be. These symptoms were different for each individual and it was essential that we were able to recognize them to avoid in-flight oxygen emergencies. When I graduated from Navigator Training in 1972 this training was required every 3 years, and during the course of my flying career I endured it 5 times. It was not high on my list of things to do and even though I had done it several times, I always approached it with some apprehension.
Perhaps part of this was due to the training profile, but much was due to the uncertainty of what could happen. As part of the pre-chamber sessions possible bad outcomes were thoroughly briefed and were always in the back of my mind.
The profile was designed to take us up to 35, 000 feet to experience the feeling of low pressure on the body and the use of the oxygen mask – later this was changed to 43,000 feet as training aircraft flew higher.
Then descend to about 25,000 feet where the mask was removed and we attempted to do several tasks which included simple math problems, writing a sentence, signing our names. As the effects of low oxygen took their toll, I began to feel light headed, unfocused, and my vision began to dim. These were my symptoms – I later heard of others who became belligerent, and incapacitated. Once the oxygen mask was back on the room brightened and the colors became vibrant and my head cleared. In the chamber there were always physiological training folks to ensure that we survived this experience.
One un-intended side effect of the low pressure was the tendency of the body to expelled the gasses trapped in the intestinal tract — in other words, every trip in the chamber was like a scene out of “Blazing Saddles,” and boy did it smell. When the initial training was done we were taken back up to experience rapid decompression — an interesting experience as the chamber lost pressure and filled with fog almost simultaneously, then it was a slow descent back to ambient air pressure and conditions so that the body could stabilize itself.
That was the basics of what we did; the aftermath was often very scary. Some folks had ear blocks — we had learned how to do the Valsalva maneuver which was performed by closing one’s mouth, pinching one’s nose shut while pressing out as if blowing up a balloon. I was able to prove it worked once in combat when during a bomb drop my left ear closed up and I experienced excruciating pain. The Valsalva maneuver caused my ears to pop and relieved the pressure. In the worst cases some experienced the bends, and we were warned not to do scuba diving after chamber training.
After one session, I experienced chest pains the next day and had to undergo an EKG. It showed no heart problems, but the flight surgeon never really explained what happened. Needless to say this was never, never one of my favorite things to do. But in the end as with most Air Force survival training, it was very valuable and prepared me well for what the future could hold in a very unforgiving environment.