Now that’s going above and beyond the call of duty: Four doctors braved the dangers of Everest and scaled the world’s tallest mountain in order to study their tolerance to low oxygen levels experienced near the peak of the 29,000-foot mountain. The doctors, who had spent several weeks acclimatizing to the thin atmosphere, had the lowest blood oxygen levels ever recorded in a healthy, non-hibernating mammal. “You sometimes see levels this low in people who are dying because they’ve had a cardiac arrest,” says team member Mike Grocott…. “We were able to talk, walk, take the blood gas and think clearly with these levels” [New Scientist].
The doctors couldn’t take blood samples on the summit because conditions were too severe, with high winds and temperatures of around -13 degrees Fahrenheit. But once they descended to about 27,500 feet the doctors removed their gloves, unzipped their down suits and drew blood from the femoral artery in the groin. The samples were then carried by Sherpas back down the mountain and analysed within two hours at a science lab set up at the team’s camp [BBC News] at about 21,000 feet. Although the climbers had used oxygen tanks during their ascent, they removed their masks twenty minutes before conducting the test to avoid skewing the readings. The findings, they say, may have implications for doctors who worry about the blood oxygen levels of critically ill patients.
The doctors hope that the study, published in the New England Journal of Medicine [subscription required], will provoke new research into the level of oxygen deprivation that patients can tolerate. Grocott says that some critically ill patients may have adapted to the low oxygen levels and may not need the aggressive interventions, such as ventilation, that are currently given to get blood oxygen levels closer to normal ranges. “All these interventions carry a risk of harm and you have to weigh up the benefits versus potential damage to organs like the lungs. “Maybe we could be less aggressive in treating some of these patients” [BBC News].
Grocott says the doctors aren’t sure why they were so perky at such a high altitude, but they have a few theories. “We don’t know how people can survive at these low levels, but we believe there are cellular and molecular changes that allow people to metabolize low oxygen. It emphasizes that we’re on the very edge of the physiological envelope.” As climbers acclimatize, or adjust to the thin mountain air, they may “turn down” their cells’ housekeeping activities to preserve oxygen, Grocott says. They may also improve the efficiency of proteins that regulate how much oxygen is used to produce adenosine triphosphate (ATP), the body’s energy currency [Scientific American]. However, the adaptation isn’t enough for long-term survival in an oxygen-poor environment, the researchers say, noting that no human civilization has ever lived above 17,000 feet.
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Image: flickr / Rupert Taylor-Price