Thursday, December 29, 2011

Flying physiology

No, I don't mean the bubbles in your drink -- that'd be fizzy-ology. I mean the changes a human body encounters when flying long distances in modern airliners.

How is this related to dance? Having just flown back to Washington DC from Japan, with a flight time of 12 hours, I'm particularly aware of the effects on my body. These effects (combined with having not slept in 23 hours) convinced me to skip a ballet class I'd hoped to attend. And... it's my blog. So there!

The air pressure at sea level is about 14.7 psi, and decreases at greater elevations. Modern airliners pressurize their cabins to about 8,000 feet above sea level, which is about 10.9 psi. This means the air pressure on your body decreases by about 3.8 psi while you're at altitude. This has a number of effects on your body.

The first is that there isn't as much oxygen available to your body. Each breath contains fewer oxygen molecules, so you'll find yourself automatically breathing more deeply and or more rapidly to compensate. Couple that with the odd head positions that result from trying to sleep sitting up and you may find yourself with a hypoxia headache, which is a major component in a hangover. Fuuunnn.

Another factor is that your body may swell a bit because of the reduced pressure. I have a particular pair of pants I often wear when I'm flying; due to a mistake I made while shopping, they're a size too big for me. Although this risks dropping trau by accident while going through the airport scanners without my belt, they remain very comfortable even at the end of long flights. I also loosen my shoes for additional comfort.

I rarely notice this on short flights, and occasionally notice it on transcontinental flights (which take about 5 hours). Getting out of your seat and moving around in the cabin is a good idea, and is especially recommended on flights longer than 4 hours to minimize the risk of DVT (deep veinous thrombosis, or blood clots in the large veins of the legs). In the case of my 12-hr flight home from Japan, I noticed significant stiffness in both legs and both ankles from about the 6-hr point on. Even doing stretching exercises periodically during the flight, this persisted to some extent until we descended for landing, and then to a lesser extent for several hours afterward. I'd taken off my shoes (ankle-high light hiking boots) during the flight and had to significantly loosen the laces to put them back on.

Quite frankly, the extent of this alarmed me. I'm a seasoned air traveler (I have Premier Elite status). I take yoga, bicycle, hike, and take ballet classes on a regular basis. Yet I'm giving serious thought to wearing medical compression stockings on longer flights (> 4 hrs) from now on.

1 comment:

  1. Well, I did it again, only this time it was 15-hour flights to/from Hong Kong. Someone, please, hit me before I do this again.

    This time, though, I wore Jobst compression socks. The doctor who recommended them commented, "When they start feeling comfortable, it's time to toss them because they're worn out". No kidding — they don't hurt, but they're not comfortable. But I didn't feel anywhere near as stiff or swollen as I did coming back from Tokyo, despite the flight been hours longer. I'll call that a success.


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