Elite climbers are testing the limits of the human body on top of the world's tallest peaks. Bruce Johnson, a professor of medicine and physiology at the Mayo Clinic, accompanied the recent National Geographic 2012 team expedition to Everest to learn more about the effects of high altitude on premier athletes—and came back with some surprising research.
Conrad Anker—the climber who found George Mallory's remains on Everest in 1999, 75 years after the explorer had vanished—led the National Geographic expedition team. (Watch a video about his discovery of Mallory.) He was the oldest climber on the team and the only member who chose to summit the 29,035-foot (8,850-meter) peak without supplemental oxygen.
Some previous studies have suggested that at high altitude (over 15,000 feet or 4,572 meters), the lungs gain fluid—extravascular lung water also known as interstitial edema. However, Johnson and his team found little evidence for this in these elite climbers: Their lungs actually appeared to clear fluid rather than gaining it. (Read “Maxed Out on Everest: How to fix the mess at the top of the world” in National Geographic magazine.)
Even so, high-altitude pulmonary edema, or fluid accumulation in the lungs, is one of the main medical causes of death on Everest. The other is high-altitude cerebral edema, inflammation or fluid in the brain. Acute mountain sickness is another threat, but it is less dangerous, often appearing as a moderate to severe headache.
"It's been somewhat controversial as to what happens at altitude and what happens to the regulation of fluid that normally is involved with various processes in your lungs," Johnson said. There may be a mild increase in lung fluid that stays below the threshold of causing health problems in many climbers, but "when we've mimicked high altitude [at the Mayo Clinic] using tents and low-oxygen gases, we've actually observed the opposite," Johnson said.
"Our studies in the laboratory suggest that when high-altitude conditions are simulated, the normal response is minimal change in [lung] water. There appears to be only a few somewhat susceptible people who are more likely to get pulmonary edema," Johnson said. He theorizes that the lung clearance among this expedition's climbers may be related to the production of catecholamines, such as adrenaline.
"One of the risk factors for edema, or fluid in the lungs, seems to be how much your blood vessels in your lungs constrict when you go to altitude," Johnson said. If the lungs can "recruit more capillaries," as he says, or increase the surface area of the lungs by popping open new capillaries as the blood flows from the heart, it helps keep the pressure down, and a person may be less likely to develop lung fluid.
Lung Size Matters
Members of the NG team—which also included climbers from the North Face and medical researchers from the Mayo Clinic—ranged in age from 25 to 49 years old. Even though Anker, at 49, was the oldest member, he did the best in terms of overall improvement related to his maximal oxygen consumption after the climb, Johnson found.
"If you laid out the average healthy adult's lung surface, it would stretch to the size of a tennis court," Johnson said. "In elite athletes, such as Anker, their lung surface area is more like the size of one-and-a-half tennis courts."
"We don't think the lungs are trainable, for the most part; it's not like the heart [which is more adaptable to change and exercise]. If you exercise a lot your lungs don't get bigger," Johnson said. "You find this [special ability] in people who have a genetic endowment or have been born and raised at altitude." (Watch a video with Johnson at Everest Base Camp.)
Time at Altitude or Genetics?
Anker has been passionate about mountain climbing since he was a teenager. "I have always wanted to be in the mountains as much as I could; I include that to be wilderness, canyons, lakes," Anker said. "I'm allergic to cities."
Unlike the Sherpas, who grow up near Everest, Anker was not raised at altitude. He was born in the San Francisco Bay area near sea level. He and his family moved all over the world, including Frankfurt, Hong Kong, and Tokyo. Anker did go to high school for two years in Colorado, however, and he also spent summers hiking with his family in the Sierra Nevada Mountains, which range in elevation from 9,000 to 14,000 feet (2,743 to 4,267 meters). He later attended college in Salt Lake City, Utah, which is over 4,000 feet (1,219 meters) above sea level.
At 14, he began technical rope climbing. But it wasn't until 1999, at the age of 36, that he climbed an 8,000-meter-plus peak (about 26,250 feet) when he climbed Everest in his search for Mallory. Only 14 peaks in the world are 8,000 meters or more.
"I think Conrad is genetically lucky and somewhat self-selected. He enjoys high-altitude climbing and has found that he's good at it. That's why he keeps doing it," Johnson said. "Conrad is tall and lean, and lung size is somewhat related to body height. We don't know how much is related to Conrad's extensive time at high altitudes [versus genetics]."
Climber Conrad Anker, at Mt. Everest base camp, describes the Mayo Clinic testing he participated in.
(*Climbing video shot from various locations)
Today Anker lives in Bozeman, Montana, at 4,800 feet (1,463 meters), but he often climbs up to 10,000 feet (3,048 meters) in the surrounding mountains.
Lung health plays a significant role in how a person feels, Johnson said. Blood flow, output from the heart, and gas exchange contribute to how a person feels, physically and mentally.
Anker has seen overwhelmed and ill-prepared climbers mentally break down and lose physical energy on Everest that could otherwise be used for their ascent. "When you're nervous you can lose a tremendous amount of energy just freaking out," he said. "That nervous energy translates into a caloric deficit."
Anker stays in shape by maximizing his time outdoors and climbing at altitude with a heavy pack. He runs regularly, does yoga, and also makes time for sit-ups and pushups, whether he's at home or in a hotel room.
To train for his recent Everest climb, Anker would switch between aerobic and non-aerobic training during a single workout. "I'd try to hike as fast as I could, do the maximum level," Anker said. "Then I'd switch to do more controlled anaerobic ice-climbing."
Bringing Back the Science
Johnson believes that there are both positives and negatives to high-altitude exposure, and he's working to apply some of the positives he learned from the elite climbers back to patients with clinical syndromes living at sea level. Heart failure, chronic obstructive pulmonary disease, obstructive sleep apnea, and forms of hypertension are among the diseases that might be treated.
"If you have small amounts of exposure, there may be some benefits," Johnson said. It could stimulate red cell production and oxygen-carrying tissues, in addition to stimulating certain pathways and enzymes in muscle. Time spent at high altitude may help the body regulate blood flow better.
Johnson is also working with the U.S. Air Force to apply some of his research to help pilots, who may be susceptible to periods of low oxygen. "We think there's some carryover from the work we did on Everest that could be used as a countermeasure for pilots, so we're starting some studies related to this work," he said.
"That's part of our goal: to take what we learn about athletes in extreme environments and translate this back to other conditions and patient populations," he added.
Editor's Note: The National Geographic Society is celebrating the 50th anniversary of the 1963 American Mount Everest Expedition and the 2012 Legacy Climb in a new book entitled The Call of Everest: The History, Science, and Future of the World's Tallest Peak.
National Geographic is bringing together astronaut Buzz Aldrin and mountaineer Conrad Anker for a Google+ Hangout on Monday, May 20, at 2 p.m. ET (7 p.m. UTC).