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Brownie Schoene Brownie Schoene, M.D.

Brownie Schoene is a physiologist with the Division of Pulmonary and Critical Care Medicine, Harborview Medical Center, at the University of Washington in Seattle.

NOVA: Is the Death Zone on the summit of Everest—is that the limit? Do you think we could go any higher?

Schoene: Well, for years it was debated whether humans could even go to the summit of Everest, but serendipitously the summit of Everest, which is the terrestrial limit of the Earth, is probably very, very close to the physiologic limit, and that we can put numbers on, and we've done that for years, at least the past 15 years. The amount of oxygen that's available at 29,000 feet is so low that the body's capability to adapt to that, to breathe enough, to get enough of a cardiac output, a heart's output of blood and so forth is—there are limits. And I think that if, for instance, we had bad weather one day and the barometric pressure was 15 or 22 millimeters of mercury and lower, Everest could not be climbed without supplemental oxygen. The fact that it's right there at the limit is—I don't know if it's the Death Zone or it's something above which, maybe 10 or 20 or 50 feet more people could go, but not much more.

NOVA: Let's talk about adaptation. How does the adaptation we've seen in humans at a high altitude apply to what you see in the Intensive Care Unit?

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Schoene: Adaptation is really critical because whether it's in the Intensive Care Unit where I spend most of my time here, where the body is stressed with diseases—heart disease, lung disease and so forth—where the oxygen level is low, or whether it's above 20,000 feet or above 25,000 feet, certain adaptations have to take place. The breathing response has to be intact. The blood response, particularly at high altitude, has to be intact so that the blood can carry more oxygen and then the tissues have to be able to utilize the low oxygen better. The mitochondria, the small capillaries in the muscle beds, have to be augmented and all those capabilities have to adapt. And that's sort of a strand in the fabric of what I've done for 20 years in the intensive care unit that I can relate. It's all physiology. It's all the same questions. The adaptations are a little bit different. The capability to adapt is different in each of those situations, but it's the same theme.

NOVA: To what extent is this adaptability actually killing us at altitude? When does it go too far?

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Schoene: The question that's been asked for a long time is, is there an altitude above which the human cannot adapt? And if you look at populations or civilizations in the world who live at altitude, there seems to be a ceiling. It may be 16, 17,000 feet at the most where people can live, thrive, reproduce, and so forth in terms of population. The high-altitude climber doesn't stay at those altitudes for more than days, weeks—so that he or she doesn't fully adapt to those altitudes of 20, 24, 29,000 feet. The body is trying to get there and never really gets there, and with enough time will deteriorate.

NOVA: What more do you want to learn in the near or far term about altitude and humans' adaptability?

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Schoene: I think that we've gotten a lot of answers over the last 50 years, certainly over the last 15 or 20 years, which have helped us to understand the adaptations. But there is still, as in most areas of science, exciting areas that we want to pursue. I think, one, we want to understand the cell a little bit better, the muscle cell, the small capillaries and blood vessels that deliver oxygen to the tissue. Those adaptations are not very well understood. Is there a limit? The other thing that is really intriguing, since the heart and lung have been studied quite extensively, is the brain. And I think that we still don't know what really stops someone from exercising more vigorously at extreme altitude. Yes, the oxygen level is low, but oxygen does get to tissues—but is there an effective oxygen [level] in the brain that then tells the body, "Listen just don't go any more?" And I think that's a critical question that is wide open to be answered.

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