February 23, 2007

Physiological Training (Episode 1)

So much to tell; infinite blogspace to tell it in. The high altitude physiological training at Andrews AFB this week was a blast. I learned a lot and had fun (despite being scared as well). Class began at 7 am Monday morning. Primarily we learned about hypoxia. Hypoxia is essentially an oxygen deficiency to your blood and brain. It can cause many symptoms which can differ from person to person and can lead to loss of consciousness and ultimately death. Now, at high altitudes pressure decreases. Therefore, with each breath you are actually taking in less oxygen than at normal pressure - this causes hypoxia. The idea behind our training was to allow us to learn about hypoxia and recognize the situations and symptoms which could lead to its onset. We also learned how to avert its dangers (so as not to die).

One of the main concepts we learned during the morning classes was the "time of useful consciousness" or TUC. When someone passes their TUC, they do not immediately pass out; rather, they becomes unresponsive and basically... useless. Also, they get a big stupid grin on their face. Since at higher altitudes there is less oxygen in each breath you take, a person's TUC decreases as elevation increases. At 35000 feet for example - where most commercial planes fly - the average time of useful consciousness is 30-60 seconds. Thank God for cabin pressurization! At 25000 ft. the average TUC is 3-5 minutes. Keep in mind: this is the altitude at which they had us take our oxygen masks off. But we'll get to that later.

Easily the most entertaining part of the class came when we got to watch videos of people (in a controlled environment) going hypoxic and passing their TUC. My favorite video was of a hypoxic man who had been given a deck of cards which he was to look at, show, and name one at a time. The exchange went something like this...

[Man shows 4 of clubs]
Man: 4 of spades.
Flight Doc: Look at that one again. Are you sure?
[Man looks again and shows]
Man: 4 of spades.
[Man puts down card and draws 8 of hearts]
Man: 4 of spades.
[Man puts down card and does not draw a new one, but displays an empty hand as though he were holding a card.]
Man: 4 of spades.
Flight Doc: Sir, can you describe what you're feeling?
Man: 4 of spades.

I absolutely lost it while watching this video. Of course, I felt slightly like a schmuck because none of the air force guys in the training were laughing - but whatever. Unfortunately there are no hypoxia videos quite this funny on YouTube.

After lunch the real fun began. We entered the chamber. After checking our oxygen equipment and pre-breathing oxygen for a half-hour (so as to avoid the bends) we began our ascent up to 35000 feet. Along the way, I learned a couple of things. First of all, remember all that pV = nRT nonsense you learned in high school chem? Definitely true. For one thing, as pressure decreases (which it did greatly during ascent) temperature decreases. By the time we got to 35K feet, I was freezing my nips off. The other crazy thing is that as pressure decreases, volume increases. Now before you go thinking I'm a dork for telling you all this, think for a moment about the gas contained in your stomach and bowels. As you go from sea level to 35000 feet, that gas expands like crazy. So, needless to say, there are absolutely no social graces in the altitude chamber when it comes to flatulence. And I absolutely will not admit that I had Taco Bell for lunch that day. Thankfully we couldn't hear or smell a thing.
Here's probably the weirdest thing that happened on our way up: when a person goes above roughly 26000 feet, their breathing cycle reverses. Allow me to explain. Currently, when you breath, you have to actively (even if practically subconsciously) take a breath in, but the breath out happens passively as a reaction to the fact that you have full lungs. Above a certain altitude though, the reverse is the case. At this point, air is forced into your lungs with no effort whatsoever and you have to forcefully exhale. (Did I make sense?) It was so freaky. It took me a while to get the hang of it actually and I think I started to hyperventilate a bit.

On the next episode of Physiological Training, descent to 25,000 feet and the dropping of the oxygen masks. Stay tuned.


Nobrainer said...

The reversed breathing cycle thing made perfect sense. Sounds awesome.

Anonymous said...

Sounds really cool. Your brother is going to be totally jealous!

Anonymous said...

As a joke they used to keep green jelly beans in a jar inside the chamber and tell people they were antigas pills. Ironically, there are green pills now that are for gas. hehe