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Hypoxia Isn't Just Hype

by Paul Engstrom, Aviation Writer and IFA Member

As student pilots, we all learned a few facts about the dangers of thin air and what the Federal Aviation Regulations require in terms of supplemental oxygen above 12,500 feet.

'Hypoxia?' I remember thinking then. 'A non-issue for me'I don't fly that high in the Cessna 172.'

But after I got my private pilot license, I read more, curious about the physiological effects of too little oxygen at altitude. And the more I read, the more alarmed I became.

I learned that hypoxia can ruin your whole day when you fly as low as 5,000 feet at night. The potential hazards alarmed me so much, I enrolled in a one-day aviation physiology class the Civil Aerospace Medical Institute offers at U.S. Air Force bases around the country (for details, call 405-954-4837.

Two other factors in the hypoxia equation were equally scary:

(1) The altitude at which hypoxia kicks in'causing symptoms such as headache, lightheadedness, nausea, tingling fingers and toes, numbness, limp muscles and impaired judgment'not only varies among pilots, but in the same pilot depending on his or her physical condition at any given time. I don't have a clue what my altitude threshold is.

(2) The more physically and mentally incompetent you get because of hypoxia, the more indifferent you feel about circumstances'the exact opposite, from a safety standpoint, of what you should feel. Some pilots even feel euphoric. Call it Deadly Rapture of the Skies.

Hypoxia occurs when the oxygen-carrying capacity of red blood cells is somehow diminished. Though oxygen makes up 21 percent of air at all altitudes, there's less air higher up, and thus less oxygen reaching your brain, which may shut down'permanently'if it's starved too severely.

Two common culprits aside from altitude are alcohol and carbon monoxide in cigarettes: They essentially bump oxygen from its seat in red blood cells. Again, that means less oxygen for the brain.

Drugs, hypoglycemia, anemia, fatigue and poor physical fitness also can lower your altitude tolerance.

It may sound like a broken record, but the best weapon for fighting hypoxia is prevention. Eating nutritiously, staying fit and avoiding alcohol and tobacco are a good start.

Aloft, a comfortable cockpit temperature is important because temperature extremes increase your body's demand for oxygen, thereby boosting your susceptibility to hypoxia. Supplemental oxygen can be a lifesaver.

I've never experienced hypoxia. But I believe the experts who say it isn't just hype. In any case, I don't want to find out the hard way.


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