Peak Performance

Doctors Scale Mountains To Research The Body's Response To High Altitudes

By David Schneider

Perched precariously at 14,954 ft on a mountain ridge straddling the Swiss-Italian border, the Capanna Regina Margherita is the highest building in Europe. From that perch is a view of the Matterhorn and other peaks in the Alps, including Mt. Blanc. At night, the city lights of Turin and Milan twinkle far below, says Erik Swenson, professor of medicine at the University of Washington.

Swenson and his European colleagues transformed a section of the Capanna, a three-story hut, into a makeshift laboratory to study the human response to high altitudes. Twenty-two human subjects were recruited primarily from Swiss and German alpine clubs to ascend to the Capanna, part of the way by cable car and the rest by a four- to six-hour climb.

About half of the subjects had previously contracted High Altitude Pulmonary Edema (HAPE), a leakage of fluid into the lungs, and so it was nearly certain that many of those would get sick on this trip: Just what the doctors were hoping for.

At the elevation of the Capanna, atmospheric pressure is less than 60 percent that of sea level, although the atmospheric composition is unchanged (21 percent oxygen, 78 percent nitrogen). At 29,035 ft, the summit of Everest, the pressure is less 30 percent that of sea level. Oxygen molecules are spaced farther apart. With every breath, less oxygen gets into the lungs. Your body can respond by breathing faster and deeper, eventually producing more red blood cells, but it cannot reach the oxygenation that it has in the lowlands.

High Altitude Pulmonary Edema is one of three major illnesses associated with low oxygen levels that can afflict travelers to high altitudes. Acute Mountain Sickness (AMS) is the most common condition. It has symptoms consistent with a mild brain swelling or injury. These include a headache with nausea, dizziness, or a generally poor feeling. High Altitude Cerebral Edema (HACE), some doctors believe, is an advanced form of AMS. It is associated with swelling of the brain and excess fluid around the brain. HAPE, Swenson's specialty, is the best understood of the three illnesses.

HAPE and HACE can be fatal if immediate treatment by drugs, or better yet, by descent, is not attained. Previous history with an altitude illness is the best indicator that someone would experience the condition again, Swenson says.

When planning to climb, people should strive for peak aerobic fitness, recommends Robert Schoene, a longtime professor of medicine at the University of Washington who has bagged many peaks himself. Schoene participated in a medical research expedition to Everest in 1981, shortly after completing a pulmonary fellowship at UW. He is now at the University of California, San Diego.

Top fitness means you'll be safer, move faster, and enjoy it more, Schoene says. "But that won't predispose you more or less to get altitude illness." Only a few elite mountaineers, including Seattle climber Ed Viesturs, have climbed high peaks like Everest without supplemental oxygen. Swenson says that's a "marvelous accomplishment" that requires fantastic mountaineering skills and luck in the rate of ascent. It's not clear that elite mountaineers have any physical attributes that set them completely apart from otherwise fit, healthy people, says Swenson. But with time, our bodies can adapt to low oxygen and learn to use it more efficiently.

All of the climbers ascending to the Capanna were non-professionals: sixteen men and six women, aged 24 to 52 years. The climb was timed like a typical ascent of Mt. Rainier. First, there was an overnight stay at about 10,000 ft, then a morning push to the summit. Although Rainier climbers frequently develop symptoms of AMS, the more serious conditions HAPE and HACE are rare. Onset of AMS occurs in only a few hours, but HAPE takes another day or more. Rainier climbers do not linger high on the mountain for this long unless stranded by bad weather or an accident.

Capanna Regina Margherita climbers, by agreement with the doctors, planned to stay at the summit for three to four days. On the way up, they had to face typical climbing conditions: hypoxia (low oxygen), cold, strenuous exercise, and the challenges of group climbing psychology. At the summit, though, they were treated to beds, electricity, and plenty of food. But nothing could be done about the thin air.

Within the first day on the summit, three climbers developed HAPE, and six more developed the illness on the following day. Even the doctors' team had some problems. A technician became incapacitated and bedridden within 24 hours with a splitting headache.

"We decided to use Dexamethasone just because I was a bit worried he was really quite ill," Swenson recalls. The patient took the drug, which has been used to treat AMS and early stages of HACE. "And within about three hours, he was out of bed, working with us, eating again, and for the rest of the three weeks he was up there doing fine."

Both the sick and the healthy climbers were subjected to a series of tests, the results of which were compared between the groups. Tests included chest X-rays, pulmonary artery pressure checks, and red blood cell counts. Doctors extracted fluid from the lungs of ill patients.

In a facility with all of the equipment necessary for medical triage and support, and with the possibility of evacuation by helicopter, all of the climbers survived the ordeal.

Until Swenson and his colleagues published their results in a 2002 issue of The Journal of the American Medical Association, doctors debated whether the leakage of fluids from capillaries into the lungs was caused by high pulmonary artery pressure from the constriction of the pulmonary blood vessels or by inflammation in the lungs. Finding no signs of inflammation in the nine climbers who developed HAPE, the team concluded that HAPE was due to high pressure in the pulmonary arteries.

One strategy that climbers can use to reduce their chances of becoming sick at high altitudes is acclimatization. Climbing slowly, no more than 1,000 to 1,500 ft per day when at very high altitudes, is a mantra among mountaineers. During this time, breathing rate increases in order to bring in more oxygen, and the concentration of red blood cells, which carry oxygen throughout the body, increases. If you go slowly enough, the blood vessels in the lungs can strengthen and tolerate the higher pressure, Swenson says, reducing your susceptibility to HAPE.

If symptoms of AMS are present, climbers should rest and wait for the symptoms to cease before ascending further, according to Thomas Dietz, writing for the International Society for Mountain Medicine. Another golden rule, he writes, is: "If you are getting worse (or have HACE or HAPE), go down at once."

Some native populations, notably in Tibet, the Andes, and parts of Africa, have lived and thrived at high altitudes for generations. Sherpas, for example, are natives of the Himalayan area who are relied upon to carry loads for mountaineering expeditions. Schoene's research has included investigations of native populations in Tibet and the Andes, where people commonly live at 12,000 to 15,000 ft. Of these groups, Schoene says, the Tibetan natives have done the best. They have lower chronic illness, no heart failure, and no overly thick blood. In contrast, the Han Chinese, who now inhabit Tibet, have more viscous blood with extra red blood cells.

In the Andes, high altitude Peruvian natives are not as well off as Tibetan natives, Schoene has found. They too have thick blood and more health problems. Evolutionary and genetic differences could be at play. "Asian high-altitude natives have been there for many more thousand years than the Andean,” Schoene notes. Still, it is not known exactly what sets them apart from lowlanders. "You develop mechanisms of improving blood flow to the tissues, and you generate more capillaries," Swenson says of adaptations over years to generations. "There are levels of adaptation in the cell itself: the control of metabolism and some of the enzymes that allow for the more efficient use of oxygen."

Compared to AMS and HACE, HAPE is relatively well understood, according to Schoene. However, Swenson's ongoing research hopes to settle yet another debate. Some scientists are promoting a theory that three-quarters of all climbers have mild pulmonary edema, that is, maybe most lungs leak at high altitude. Swenson's team doesn't buy that argument.

In an attempt to put this debate to rest, Swenson and his colleagues are reestablishing the laboratory at Capanna Regina Margherita in the summer of 2005. This time, to supplant the old X-ray machine, Swenson will equip the lab with new technology, a CT scanner. The device takes X-rays from several angles, from which computers develop a three-dimensional picture of the inside of the body, at ten times the resolution of conventional X-rays. "We want to find out where in the brain and in the lungs you see the first leak," Swenson says. The team intends to take a closer look at the lungs, and to determine whether or not AMS symptoms are due to subtle brain edema that cannot be picked up by other methods.

To transport the large machine to the Capanna, the team won't be hiring Sherpas. The scanner will be flown up by helicopter in five pieces and assembled on site.

David Schneider is working on a Ph.D. in earth and space sciences at the University of Washington.

Images:

Top: The Capanna Regina Margherita. Photo courtesy of Erik Swenson

Chest X-ray of a patient with HAPE on left. The cloudy area near the center is caused by fluid in the lungs. At right, the fluid that was extracted from the lungs by doctors at the Capanna. Images: Erik Swenson

For more information: Books on high altitude medicine recommended by Erik Swenson include The High Altitude Medicine Handbook by A. J. Pollard and D. R. Murdoch, and High Altitude Medicine and Physiology by J. S. Milledge, J. B. West, and M. P. Ward. For a jumping-off point on the Internet, try the International Society for Mountain Medicine, www.ismmed.org