Surviving the Extremes: A Doctor's Journey to the Limits of Human Endurance (32 page)

In the morning the surviving climber left his lifeless partner in the tent and came back down the ropes. He passed the body of the other exhausted climber, still resting in his harness, frozen to death.

“He was our expedition leader,” the climber told us. “His dream was to climb Everest.”

A dream may spring from the mind, but it needs a brain to contain it and a living body to sustain it. For the expedition leader, the dream was extinguished when the chemical sequences stopped and the fires went out. As for the rest of us on the mountain, our bodies were still more or less protecting us from our surroundings, incubating all the chemical reactions that create heat, heartbeat, motion, emotion, ideas, and dreams.

It’s uniquely human that the most subtle of those reactions—the ones that produce (or perhaps form as the result of) our abstract thoughts—are able to override our most powerful instincts for self-preservation.
A human body can be motivated to take risks not just for practical necessities, such as finding food or escaping predators, but on behalf of abstract concepts like scientific curiosity, adventure, and individual achievement, which have nothing to do with survival. When the most highly developed part of the brain, the frontal lobes—the seats of judgment, thought, and will—give a command to enter a hostile environment, the rest of the body suppresses its survival instinct and dutifully carries out the command, protecting itself from the results as best it can.

Human bodies vary enormously in their ability to withstand cold. The Yaga Indians of Tierra del Fuego don’t wear clothes, even in winter, and the women have been known to calmly breast-feed their infants in open boats during ice storms. Aborigines in Australia and Kalahari bushmen in Africa are able to sleep naked on the ground during freezing desert nights. These desert dwellers have developed the same tactic as camels, though applied in reverse: they allow their body temperature to move several degrees closer to the outside temperature, making body temperature that much easier to maintain, since the differential has been decreased. Camels save energy by not sweating, allowing their temperature to rise during the day. They retain the excess heat until evening, when the desert breezes cool them off again. For the human desert dwellers, who can’t store heat the way camels do, the same cold night breezes pose the threat of hypothermia. They save energy by not shivering, lowering their metabolism, and allowing their temperature to fall overnight to as low as 95°F. It’s almost a minihibernation. These people awaken with no adverse effects and let the morning do the work of rewarming them.

The rest of us can’t get away with this. We would become hypothermic and perhaps not get up at all. How some people do it is something of a mystery. It may well involve the same chaperone proteins that increase heat resistance in marathon runners. The formation of these proteins is stimulated by cold as well as by heat, and once formed they will prevent other proteins from being deformed, or “unfolded,” and inactivated by cold. Such tolerance does not appear to be due to any inbred gene; rather, it stems from maximizing the body’s ability to adapt to cold through repeated exposures. Before his Antarctic
traverse, French explorer Jean-Louis Etienne would begin shivering as soon as his body temperature started to drop, just like any other Frenchman. On his return, however, he discovered that he could tolerate a body-temperature drop to 95°F before shivering commenced. Though the exact mechanism remains mysterious, the idea that the body can “learn” to tolerate cold has been an extreme medicine assumption for a long time. In preparation for their voyages, early Arctic explorers were advised to take cold showers—increasing their duration and decreasing the temperature every day until departure. Further advice was to stop washing as soon as they had left. Dirt accumulating on skin helps the body retain heat. This advice has also proven to be true, and I know from experience that it’s one rule mountaineers have no trouble following.

Eskimos are the premier cold weather adapters. Besides having their share of those chaperone proteins, they have a thick layer of subcutaneous fat that provides extra insulation. This seems to be a response to the environment rather than an inbred characteristic. People in temperate climates often take on weight during the winter and lose it during the summer. Eskimos tend to retain it. With animals being virtually the only food available, an Eskimo’s diet is rich in animal fats, which, when metabolized, not only provide a great source of heat but can be easily converted to human fat and deposited below the skin. Living in such a harsh environment with such limited resources, Eskimos are provided with the only fuel efficient enough to allow them to survive there.

Eskimos also benefit from their shape. They have a compact design with short arms, legs, fingers, and toes. They’re styled for the Arctic much the same way penguins are styled for the Antarctic. However, humans can’t compete with animals in the extent of their adaptations. Our muscles stop contracting below about 70°F for example, whereas the muscles of the arctic fox continue to work down to nearly 0°F. Caribou have fat whose composition varies with its location. Within the body proper, the fats are saturated—like butter, able to remain liquid only when the temperature is high. As the fats become more exposed, such as they are in the legs, they become progressively more unsaturated—like olive oil, which doesn’t freeze even at low temperatures.
No animal can beat the wood frog, though. When the temperature drops below zero, the animal freezes. Then, when the temperature rises again, it simply thaws out and goes on about its business.

Evolution has left humans well short of matching those talents. We developed big brains instead—either because we needed one to make up for our limited physical abilities or because, once we had one, we learned to get by with what we had. Either way, humans rely primarily on behavior to survive the cold, mimicking animals and often outperforming them, using what’s available in the environment. Sherpas build stone huts and often sleep in people piles to stay warm. Eskimos build igloos and wear animal skins inside out—because wearing the fur that way traps more warm air than the way the animals do it. The ultimate human behavior modification that helps us survive cold is migration. Humans retreated to equatorial zones during the last Ice Age. Many still head south every winter to escape the cold.

That last thought seemed especially relevant to those of us who often wondered what we were doing on Mount Everest. Life at base camp was like living in a refrigerator. We had ice below and on all sides of us. The supercooled, superdry air circulated over the ice and then through our lungs. Each breath had to be warmed to body temperature and moisturized to 100 percent humidity to keep the lungs happy. The heat and water required to do this were far more than our bodies could provide, so our air passages, the trachea and bronchi, became irritated and dry, giving rise to what climbers call the “Khumbu cough.” Everyone who climbs Everest gets it. Though I handed out throat lozenges and cough syrup and told everyone to breathe over a pot of steaming water, the only real cure is descending. Had I sent down everyone who had a cough, there would have been no one left to climb. But had I not sent anyone down, at least temporarily, some would have been debilitated from the repetitive spasms, a few would have broken ribs from the forceful exertion, and one or two would have died from pulmonary edema.

It was no easy job to sort through the chorus of coughers who collected for dinner each evening, making the mess tent sound like a tuberculosis ward. On one particularly noisy night, after I had listened
with my stethoscope to all the loudest coughers, I handed out a lot of medication. Everyone seemed to need it. Even our kitchen boy, Koncha, who had been working hard around our table all night, asked for pills. I hadn’t heard him cough even once but gave him some pills anyway, thinking that he just wanted some attention.

Just before sunrise, I was awakened by an urgent shout just outside my tent.

“Dr. Ken! Come quick, come now!”

Outside, I found our cook, Ong-Chu, pointing to the kitchen tent with one hand, pointing to his chest with the other, and shaking his head. I entered the kitchen tent and, in the yellow light of the lantern, saw Koncha. He was in his usual sleeping spot, a mat in the far corner of the tent, but was sitting upright, making great heaving efforts to breathe. Even from across the tent I could hear wet bubbling sounds coming from his chest. His breathing was shallow and rapid, interrupted by violent bursts of coughing that brought up blood-tinged globs of frothy mucus. His lips were puffy and blue, his skin was clammy and pale, and his eyes were wide and terrified. This was pulmonary edema—a high-altitude killer. In the early days of extreme medicine, it was thought to be caused by the breath of dragons lurking behind high mountain passes. Since the discovery of oxygen, however, this theory has been largely disproven, although we’re still not sure exactly what causes it. Pulmonary edema only occurs at altitudes above 8,000 feet, and while it comes on suddenly, it does so only after its victim has been there at least a few days. Usually it develops from a cough or after heavy exertion, and rapidly worsens at night or in bad weather, making treatment and evacuation to a lower altitude all the more problematic.

Healthy lungs have it easy at low altitudes, where there is more than enough air pressure to fill the alveoli and drive oxygen into the blood. Lungs take in far more oxygen than they consume, and thus provide a large surplus for every other organ in the body. They even have room to spare: there is so much excess capacity that many alveoli remain closed during normal respiration. As altitude increases, however, the consequent drop in pressure makes the lungs work harder. When the blood and then all the other organs signal the hypothalamus
that they aren’t getting enough oxygen, the hypothalamus forwards the complaints to the lungs. As altitude increases further, the complaints get louder and the lungs become the most put-upon organ in the body. Their first reaction is to breathe faster and deeper. This out-of-breath response speeds up air intake and opens dormant alveoli. To benefit from the increased airflow, the lungs must keep pace by increasing the blood flow to match it. This they do by turning up the pressure in the pulmonary artery, the conduit that carries blood from the heart to the lungs. To make oxygen intake more efficient, the lungs also have another mechanism, one that works well at sea level but backfires at high altitude. Blood flow through each section of the lung is monitored for oxygen content. Where alveoli are not providing enough oxygen, blood vessels constrict so that flow can be diverted to more “productive” areas. This feedback system evolved to help humans get by when injury or infection damaged a section of lung. Those are threats the body understands. It doesn’t understand low oxygen pressure, however. Lungs were never designed to function at high altitude.

Faced with low oxygen readings everywhere, each section of the lung reacts as if it were the only one affected, narrowing its vessels to divert flow to some other section. But the vessels are constricted everywhere—there’s nowhere for the blood to go. To make matters worse, the pulmonary artery is delivering blood at high pressure, still trying to keep pace with the high rate of airflow. The effect is like opening the valve to a garden hose and then pinching the end of the hose shut. The flow comes through the vessels as a narrow jet, coursing into the delicate alveolar capillaries under tremendous pressure. The thin membrane wall separating the capillary from the alveolus begins to leak fluid and then ruptures like a bursting dam. Plasma, the liquid part of the blood, spills into the air sacs. The victim drowns in his own fluids.

This was precisely what Koncha was about to do unless I could stop him. He needed to be moved to the medical tent. Two Sherpas began to help him up, but I insisted he be carried, though the tent was only a short distance away over the ice. The exertion of walking would increase his pulmonary artery pressure even more.

The sun was still not up. The medical tent was dim except for
one powerful flashlight. Koncha was deposited on two foam mats propped against an oxygen crate, center stage beneath the spotlight. Kneeling down next to him, amid supplies and an audience of anxious volunteers, I took out a stethoscope, although I hardly needed one to hear the turbulence within his chest—the gurgling noise of air bubbling through fluid filled three-quarters of his lungs. Struggling to maintain blood and air flow, his pulse had doubled and his respiration rate tripled. The oxygen saturation in his blood (normally close to 100 percent) had fallen to 26 percent—a level that until then I had thought incompatible with life. Not many of his alveoli were still working. We kept him sitting upright so that the fluid pouring into his lungs would fall to the bottom, hoping that would leave the topmost alveoli high and dry long enough for the leakage to stop and the water level to recede.

The treatment is to reverse the cause—to reduce the force squeezing fluid through the capillaries into the alveoli. I placed a mask over Koncha’s face so that the air he inhaled, though still at atmospheric pressure, was 100 percent oxygen instead of the normal 21 percent. Body sensors immediately detected the fivefold increase in concentration and eased off on their distress signals to the lungs and heart. Pulse and respiration rate dropped. The pulmonary artery pressure valve relaxed. There was more oxygen around now. Nonetheless, many of the alveoli were underwater, not able to let the oxygen through. Responding to the low oxygen level, the vessels surrounding them remained constricted, so the fluid pressure against their walls remained high and they were still leaking. Koncha’s breathing remained labored, and he was still coughing up blood and bubbles. I had wanted to start an IV immediately, but that early in the morning the bags of solution were frozen solid, so I had sent a few to the kitchen for defrosting. The first ones came back. I hadn’t been wearing gloves, so my hands were too cold to judge the temperature of the bags, but by touching them to my cheek I verified that I wasn’t going to fill Koncha with ice water.