Surviving the Extremes: A Doctor's Journey to the Limits of Human Endurance (33 page)

Koncha was trembling so violently that two people had to hold him down while I inserted a catheter in his vein, connected the IV tubing, and started giving him fluids. His lungs may have been flooded,
but the rest of his body was dehydrated—in part from supplying all that fluid to his lungs. Having an IV in place made it much safer to use nifedipine, a drug that relaxes the muscles of small blood vessels. It would help relieve the constrictions that had formed in Koncha’s lungs in response to his flooded alveoli but it would also dilate vessels throughout the body. The total effect of so much lost resistance sometimes means a precipitous drop in blood pressure. In that case I would now be able to keep Koncha pumped up by adding more fluid through the IV.

With oxygen driving down the pulmonary artery pressure and nifedipine opening the vascular channels, the blood flow was slowed. The pinch was eased. Koncha’s lungs stopped leaking. His coughing subsided, the blue color left his lips, and the fear left his eyes. He was on high maintenance, though. Without the oxygen, fluids, and medication, his symptoms would come back. We had to get him out of there.

Mount Everest’s base camp is at the altitude limit for a helicopter evacuation, and for it to be possible, conditions have to be perfect—which, on that day, they weren’t. The sun was up, but the sky was overcast and it was snowing lightly. We needed to get Koncha lower—even a few thousand feet would probably provide enough air pressure to keep his lungs inflated. The plan was to carry him off the glacier, along the trails that pass through the villages. There was a small clinic located at 14,000 feet; if he wasn’t better before then we would go there.

Koncha was breathing easier now and alert, but if we let him walk, the exertion would drive his pulmonary artery pressure back up so rapidly he would collapse before he got out of camp. He would have to be carried, but until we were sure his lungs were dry, he had to remain sitting up. I was pondering how to do this, but the answer was immediately obvious to the Sherpas. A lightweight aluminum folding chair was opened and placed face-out on the back of a volunteer. Ropes were passed around the frame and tied to his waist and shoulders. Another rope was looped from the chair top across his forehead. The Sherpa squatted down so that the chair legs touched the ground, and Koncha sat down. Once Koncha was strapped in, the Sherpa stood
up, absorbing the strain fairly easily as the ropes tightened around his abdomen, chest, and forehead. Another Sherpa loaded an oxygen cylinder into his backpack, winding its hose forward around the front so that the regulator could be placed over Koncha’s mouth. He was using the longest hose we had, but staying tethered to Koncha would not be easy. Two other Sherpas loaded extra oxygen tanks along with some of my medical supplies. Our mountain ambulance was ready.

We traveled much faster than I expected. Taking turns carrying Koncha, the four Sherpas set a pace I couldn’t match. I routinely fell behind, catching up only when they stopped to exchange loads. In a few hours we were off the glacier and onto the trails. Koncha was holding his own but still dependent on oxygen. Though we had unhooked his IV for the trip, I gave him some more nifedipine. He looked as if he could use it. We hadn’t yet lost much altitude. The next part of the trail down was steeper; I hoped he would begin to improve more rapidly.

After several hours, we began to see signs of civilization—a yak, a few more yaks, a yak herder, then finally a village—Pheriche, which, at 14,000 feet, is the highest permanently occupied settlement in the Himalayas: a few stone huts and two teahouses to accommodate visiting hikers. We were greeted incredulously as we came into town by a group of young female German trekkers, resting in front of one of the teahouses. Koncha was breathing much easier now, taking only occasional puffs of oxygen and enjoying the attention he was receiving from the girls. The warm teahouse seemed like a good place to spend the night. The rooms were all taken, but there was space available on the floor. Two of the German girls made sure Koncha was fed, then arranged some mats on the floor for him to sleep on. I appreciated the unexpected nursing help and was pleased at Koncha’s improvement. Pulmonary edema often worsens at night, however, and I was anxious to see how he would be in the morning.

The first thing I did when I woke up was look over to make sure Koncha was still alive. His mat was empty. I found him in the kitchen, sipping tea and flirting with the trekkers. He didn’t speak German and they didn’t speak Nepali, but it seemed to me he was asking one of the girls for a date. Clearly, Koncha needed no further treatment. The
3,500-foot drop had brought him to an altitude where air pressure is high enough to sustain life. As long as he remained below this invisible barrier, he would be safe. If he dared to cross it again he would be courting disaster.

Koncha had been at base camp for weeks before suddenly developing pulmonary edema. True to form, it had struck at night, when the barometric pressure routinely drops; and earlier that evening he had been exerting himself around the kitchen. Bad weather had been rolling in—a front of low pressure. What that meant, effectively, was that the altitude of base camp rose. The additional drop in pressure pushed Koncha, already at the limit of his physiology, over the edge. But he had endured higher altitudes and stormier weather many times before. What happened this time? Maybe it really was dragon breath.

Leaving Koncha with his newfound friends, I reentered the realm of pulmonary edema, the no-man’s land above 14,000 feet, once traversed by Mongol warriors but now frequented more by climbers and trekkers. Over seven hundred years ago, Tibetan doctors described symptoms of “oppression of the chest” and “white froth coming from the mouth” among the Mongol invaders. They also noted, though they couldn’t explain why, that the malady seemed to attack only strangers. Modern doctors have confirmed the observations of their early Tibetan counterparts, so I was puzzled why Koncha was struck rather than a visitor like me. I should have been much more vulnerable. I made my way back up to base camp pondering this question, and watching for dragons.

When I arrived I mentioned to our cook, Ong-Chu, that I had never before known a Sherpa to develop pulmonary edema.

“Koncha is not a Sherpa,” Ong-Chu informed me. “He’s a Rai. He has been across high mountain passes many times, and he wanted a chance to make big money as a kitchen boy, so I gave him the job.”

Ong-Chu had solved the riddle. Rais are an ethnic group from the lowlands of Nepal. The Sherpas are of Tibetan stock, having migrated from the high plateaus into the Himalayas about five hundred years ago to escape those rampaging Mongols. Their ability to withstand the altitude and cold is the result of natural selection through uncountable generations, combined with maximum adaptation by each
individual acquired from a lifetime in the mountains. Exactly how they do it is still largely a mystery. Some possibilities seem obvious: larger lung capacity to augment oxygen intake, a bigger heart to circulate blood faster, a lot more red blood cells to increase oxygen-carrying capacity. But obvious answers are often wrong. The Sherpas have undergone none of those design changes. Their adjustments to high altitude are far subtler. Nonetheless, taken together, they produce a body exquisitely fine-tuned for life at the upper edge.

Sherpa lungs are not especially big or powerful, but they are very sensitive to low oxygen and will maintain an increased rate of breathing even at rest—that is, they have a higher idling speed. Sherpa hearts are not stronger, but they don’t have to be. To keep pumping, the heart muscle normally relies on fat, a fuel that doesn’t burn well in low oxygen. A Sherpa’s heart muscle can take in glucose, which it can burn 50 percent more efficiently, thereby providing the same cardiac output with much less work. A Sherpa’s blood has only a few additional red cells, but its capacity to transport oxygen is greatly increased by special enzymes that ride along with the hemoglobin to speed up the capture and release of oxygen.

Sherpas have other advantages as well. Their lungs are capable of producing large quantities of nitric oxide, a naturally occurring chemical in all human lungs but one Sherpas produce twice as much of as almost everyone else. Nitric oxide acts as a vasodilator, opening up constricted vessels in the lungs. Having a large supply might be why Sherpas at high altitudes are nearly immune to pulmonary edema.

One survival mechanism all humans share involves a preprogrammed sequence of chemical reactions called anaerobic respiration. Though it is not as efficient as normal respiration and results in the buildup of lactic acid, which has to be broken down later, anaerobic respiration provides quick energy for emergencies without using oxygen. It would conceivably provide a made-to-order system that Sherpas could exploit to adapt to their environment, and a possible explanation for why they are able to work so hard at such high altitudes. A neat theory but a wrong one. Sherpas working at maximum capacity produce less lactic acid than the rest of us, a condition known as the
lactic acid paradox
. The probable explanation is that Sherpas don’t
need to form lactic acid because they can maintain high fuel-burning efficiency even in low oxygen—by using enzymes we still haven’t identified.

When species are subdivided and isolated from one another, adaptive responses to a similar extreme environment may evolve very differently. The Sherpas of the Himalayas and the Quechua and Ayamara Indians of the Andes last had a common ancestor about two hundred fifty thousand years ago. People have been in the plateaus of Asia for at least thirty thousand years, but the Quechua and Ayamara took awhile to migrate to the mountains of South America, arriving in the Andes only about ten thousand years ago. Since then, they’ve been faced with the same environmental challenges as Sherpas, but their bodies have responded in nearly opposite ways.

The Andes natives are barrel-chested and have large lungs with extra alveoli and more capillaries. Their hearts are bigger, with well-developed muscles in the right ventricle—the chamber that pumps blood under high pressure through the pulmonary artery into the lungs. They have increased numbers of red blood cells to transport oxygen and an increased volume of plasma in which to float them so the blood doesn’t sludge. Their adaptations seem to be acclimatization pushed to the limits—mechanical changes rather than the biochemical ones of the Sherpas. They do, however, show some adaptations at the molecular level. Like the Sherpas, they demonstrate the lactic acid paradox, and their hearts utilize glucose. Their lungs produce extra nitric oxide, though not as much as the Sherpas do. However, they still do not share the Sherpas’ increased lung sensitivity to low oxygen or their special hemoglobin-binding enzymes.

But both systems—mechanical and biochemical—work, and not just for humans. There are other large mammals beautifully adapted to life in the high mountains. Sherpas share their extreme environment with yaks; the Quechua and Ayamara Indians, with llamas. Yaks have developed hemoglobin-binding enzymes similar to those of the Sherpas; llamas have strong right ventricle muscles, just as the Indians do. They don’t seem to possess the other human modifications, but they
do fine as long as they remain at altitudes that are within their physiological borders. Only humans push themselves beyond their bodies’ limits for reasons that have nothing to do with survival.

On Mount Aucanquilcha in the Andes, there is a permanent sulfur mining settlement at 17,500 feet—about the same altitude as Everest base camp. The mine itself is at 19,500 feet, but the miners find life there too uncomfortable to stay continuously. They prefer to sleep at the lower elevation, though that means a daily 2,000-foot climb. Sherpas are also unable to stay above base camp for any protracted length of time, and need to come down to recuperate after each short stay at a higher camp. Indians and Sherpas have taken different routes to high-altitude adaptation, but both seem to have arrived at the same physiological limit.

Although there are more permanent settlements at higher elevations in the Andes than in the Himalayas, the Sherpas are generally considered to be more smoothly adapted to their environment. They’ve had a twenty-thousand-year head start. If whatever variations exist between the Sherpas and the Andes natives are the result of different gene pools, the two groups’ high-altitude adaptability will continue to develop along different lines. If these adaptations are the long-term result of environmental pressure shaping natural selection and individual development, then perhaps the Indians will evolve in the direction of the Sherpas. However, the decreasing isolation and increasing mobility of both these groups make it far more likely that homogenization of genes and reduced environmental exposure will prevent either outcome.

Now that I knew that Koncha wasn’t a Sherpa, or an Indian, or for that matter a yak or a llama, I understood how he could have developed pulmonary edema, though I still didn’t understand why. Other illnesses I faced were far easier to understand—and to treat. Besides coughs, headaches, and diarrhea, two other conditions unique to this environment afflicted my expedition. One was a high-altitude toothache. Air often gets trapped inside rotten teeth that have fillings. As the outside air pressure drops, the air in the tooth expands painfully.
The treatment involves letting it out by inserting a hollow needle into the abscessed tooth. The other condition is high-altitude flatus. The cause is similar—air trapped in the many loops of the intestines expanding and forcing its way out the rectum—but the treatment is different: Pepto-Bismol and temporary isolation.

The conditions I have seen on Mount Everest have run from the mundane to the bizarre. I was about to enter my tent one afternoon when in the distance I spotted one of our Sherpa porters moving slowly and unsteadily up the glacier toward me. Heavy snow was blowing sideways against my face; it was too cold to wait outside. When the porter came into my tent he was wearing rubber thongs on his feet. He told me he had fallen through the ice very early that morning, sinking up to his knees in water. He’d had no way to dry himself off, and in fact had fallen through several more times before he reached solid ice. His feet were numb and swollen and he had lost control of his toes. “All day,” he told me, “I have been walking in someone else’s feet.”