Even those who study the effects of altitude on the human body have been stunned by the story of a 15-year-old boy who hitched a ride Sunday from San Jose, California, to Maui, Hawaii, in the wheel well of a Boeing 767's landing gear. The teenager managed to survive extreme cold and low oxygen levels on a five-hour flight.
To talk about how this young man, still unidentified, could have lived through the ordeal, National Geographic spoke with Jeff Sventek, an aerospace physiologist and executive director of the Aerospace Medical Association.
The Federal Aviation Administration reports that there have been 105 stowaway attempts in airplane wheel wells since 1947, including this latest one, and that 80 of them died.
How do people die in those conditions?
The two primary physiological and medical concerns are reduced oxygen pressure that will lead to hypoxia—people lose consciousness—and the extreme cold that leads to hypothermia.
So with hypoxia, as the body is being deprived of an adequate oxygen supply, how does it adjust to try to save itself?
Brain cells, like any other cell in the body, will die off without an oxygen supply. But by losing consciousness, the brain is not as active. The body will start trying to get oxygen to the brain more efficiently, and the brain will distribute oxygen only to the autonomic nervous system, which controls involuntary functions such as heart rate and respiratory rate.
How does hypothermia contribute to the body's urgent effort to stay alive?
Hypothermia slows the flow of blood to the extremities. With blood flow to the periphery restricted, warm blood concentrates its flow to bathe the core portions of the body, the internal organs, and the brain.
That's the effect that explains frostbite—reduced blood flow that damages ears, fingers, and toes. Yet, early reports are that the boy didn't suffer that kind of damage. How's that possible?
I can't explain it. I can only speculate. Very close to the floor of the plane or the ceiling of wheel well, there is probably a large compartment of electrical equipment. Perhaps heat generated from that equipment could have radiated through the floor, and he might have gotten his hands and feet close to it.
How perplexed are you by his survival?
I've run it through my mind several times trying to figure out what this young man could have done to protect himself and come out of this alive. For someone who spent his life teaching this and understanding it, it's still very hard for me to understand and grasp how he dropped down and was walking around the tarmac after this experience. He's just a very, very lucky young man.
You've run training sessions for pilots and other personnel to demonstrate the effects of high altitude on the human body. Could you explain those sessions?
I spent my years in the Air Force running altitude chambers and demonstrating the acute effect of breathing air at up to 35,000 feet (10,668 meters). That's as high as we were allowed to go. Flight engineers, pilots, and anyone who was going to fly for a living in the Air Force had to come through our training program.
We had a large metal box called a hypobaric chamber. We would take them in, up to 16 students and three trained technicians or officers. We would go to a simulated 35,000 feet on the first chamber flight. One student volunteer would drop the oxygen mask to demonstrate for the group how quickly the symptoms came on. Then we'd put the oxygen mask back on the student and take the proper treatment steps. We'd demonstrate the same thing at 30,000 feet (9,144 meters) and at 25,000 feet (7,620 meters) altitude.
How long does it take to lose consciousness?
At 35,000 feet, it took a half a minute to a minute. At 30,000 feet, it took a minute to a minute and a half. At 25,000 feet, it took three to five minutes.
What does the lead-up to loss of consciousness feel like in the hypobaric chamber?
The beauty of hypoxia is that symptoms tend to be consistent over time. When I experience hypoxia, my first symptom is a warm face. Then there's a tingling in my fingertips. And then there are visual problems, and you can't focus well. Knowing those three symptoms, when I went out to fly if I started to feel those things, the first thing I'm going to do is put oxygen on and then determine whether we've lost cabin pressure. The training session teaches each student what his or her symptoms of hypoxia feel like.
This interview has been edited and condensed.