Chicken soup

Highest peak in North America, the 20,310 foot sentinel stood beckoning against the northern horizon. My friend Bob Cleaves and I rushed to the airport and departed northbound in our rented Piper Archer.

Denali, like Kilimanjaro in Tanzania, is shy and elusive, frequently hiding behind a shroud of cloud, but not this day. The majestic mountain grew larger in the windshield and posed for the photographs we had hoped to take. The Archer struggled toward the summit. Finally, when it could climb no more, Cleaves suggested that I hop into the backseat and take a wide angle shot that would include him in the foreground and the peak in the background.

It wasn’t easy, but I finally made it—and then promptly collapsed for what seemed like an eternity but was for only a few seconds. I hurriedly framed Cleaves and the mountain in the viewfinder, snapped the picture, and yelled for him to descend. At 18,500 feet, my chest was pounding, and I was having difficulty recovering from the exertion.

Cleaves quickly lowered the nose and noticed that he too was having trouble breathing. Moments later, we returned to that very thin layer of the atmosphere where pilots can function normally without the aid of supplemental oxygen.

I used to think that this was my first experience with hypoxia (a shortage of oxygen), but I was wrong. I have since learned that pilots can suffer from low grade hypoxia as soon as they leave the ground. In this sense, a pilot is like a normally aspirated engine that loses performance as it climbs.

It is interesting that we readily accept the concept of an engine losing power with altitude but are less willing to acknowledge a personal loss of performance. This is because the effects of hypoxia develop so insidiously. The most common symptoms include visual disturbances, loss of muscular coordination, judgment impairment, lightheadedness, dizziness, apprehension, and a bluish discoloration of extremities. Although it might seem that pilots would recognize these symptoms, they often cannot because of what might be hypoxia’s most dangerous effect: euphoria, a strong sense of wellbeing that camouflages other symptoms. This should lay to rest any notion that a pilot can wait to recognize the symptoms of hypoxia before taking corrective action.

Although most pilots would never risk flying under the influence of drugs and alcohol, many of them expose themselves to similar dysfunctions by unwittingly operating under the influence of hypoxia. Most of what I read about hypoxia usually involves a discussion of hemoglobin, erythrocytes, alveoli, red corpuscles, permeable membranes, and other terms that only remind me of how I struggled through Physiology 101.

There are only two things a pilot needs to understand about hypoxia. The first is that he usually cannot recognize its disabling effects—particularly during periods of stress. The second is that there is only one instrument that can warn of hypoxia: the altimeter. Although the use of supplementary oxygen is not required until above 12,500 feet for more than 30 minutes and whenever above 14,000 feet for any period, these rules seem too liberal. Military instructors teach that oxygen should be used whenever above 5,000 feet at night and above 10,000 feet during the day. One pilot—who also is a flight surgeon—is so conscientious about avoiding hypoxia that he has printed in bold red the word “OXYGEN” on his high altitude power charts as a reminder to begin using oxygen at the appropriate altitude. He regards his supplemental oxygen system as a “turbocharger” that allows him to recapture the personal performance lost during climb (see “Into Thin Air,” p. 89).

Over the years, I have purchased a number of safety related items to take on appropriate flights. These include a first aid kit, a survival kit, a fire extinguisher, and—most recently—a portable oxygen system that goes along on all night cross-country flights and those daylight flights that could wind up above 10,000 feet. (I would love to have had a bottle available during my flight into La Paz, Bolivia. The elevation of the airport there is 13,300 feet msl, and I needed oxygen just to perform a walkaround inspection.)

There have been many accidents that can be at least partially attributed to hypoxia. Perhaps this is why many airline pilots don a mask and breathe oxygen prior to a night approach or when tired. Does this do any good when flying an aircraft pressurized to several thousand feet above sea level? I believe that it does. On the other hand, oxygen is a little like chicken soup. According to my mother, it can’t hurt.

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