On top of the world, just below the more than 29,000-foot high peak of Mount Everest, a team of four British medical researchers braved the elements and took their own blood samples. What they found was staggering—their oxygen levels were the lowest ever recorded, well below levels that would normally prove lethal on the ground. And while the team’s study has just been published, one of its authors tells PM that his research performed on the world’s tallest peak could help doctors treat intensive care patients struggling with low levels of oxygen in their own bloodstream.
How low can your blood oxygen level go? To find out, you might need to climb a mountain.An average person at sea level has about 13-14 kilopascals (kPa) of oxygen in their bloodstream, University College of London medical researcher Dan Martin says. When his intensive care patients drop to around 8 kPa he gets very worried, and a normal person with 6 kPa of oxygen faces almost certain death. Imagine his shock, then, when he and three colleagues on the top of Mount Everest measured their own blood oxygen level to be between 2.5 and 4 kPa, the lowest ever measured in live people.The doctors, who are also serious amateur climbers, scaled Everest last spring, and have now published their record findings in the New England Journal of Medicine. All four reached the summit, but they couldn’t take readings right at the top. “It’s always reasonably unpleasant up there,” Martin told PM–the conditions when he arrived were -25 degrees C with howling winds. So the scientists descended to a small shelter, where they could “strip off” and take their own blood samples. A Sherpa then carried them down to a makeshift lab about 21,000 feet above sea level. And as if the brutal cold and wind of the Himalayas weren’t jarring enough, Martin soon saw his team’s blood oxygen numbers. “These are staggeringly low,” he says.Martin’s expedition achieved a new record, and it could spur some scientific and medicinal advances, too. If some climbers can keep climbing with oxygen levels are ordinarily lethal, then they must have some kind of ability to “almost hibernate,” as Martin puts it, possibly conserving oxygen by temporarily suspending non-essential functions. “That may be working at the cellular level,” he says. To test that idea, the doctors also took tiny biopsies of their own muscles when they were atop Everest and froze them in liquid nitrogen. Now scientists across Europe are looking at the samples, Martin says, primarily the mitochondria–the cellular powerhouse–to see whether cells sacrifice other tasks to keep producing energy when oxygen gets scarce.As a doctor, what Martin really craves is a way to distinguish people who can switch to this “hibernating” mode and survive on low oxygen from those who cannot. Most intensive care patients have lower blood oxygen than healthy people, he says, and though they need oxygen to survive, giving them large doses of it can be dangerous or damaging to the lungs. If doctors knew that a patient could survive with low oxygen, they might let that person’s oxygen levels drift down a little more before they resort to risky treatments.
If Martin has to go back to the mountains to help find the answer, he won’t mind. He climbed some of the world’s tallest peaks in the Alps and elsewhere before tackling Everest, though not as many as he’d like. “Our clinical work keeps us away from the mountains,” he says. But with climbing mountains providing record-setting research, he might be able to get out of the office a little more often.