Surviving the Extremes: A Doctor's Journey to the Limits of Human Endurance (14 page)

There is an overwhelming profusion of life in the Amazon, and we know virtually nothing about most of the species that live there. Plants, animals, and humans are inseparably intertwined in a fabric of baffling complexity. They are totally interdependent, yet they battle each other mercilessly to stay alive. Each species is a winner; all the losers are extinct. Unraveling the secrets of their success would lead us down a labyrinthine path into knowledge of nature’s most fundamental laws of survival. And if we are smart enough to listen to the people who have been competing successfully there for twenty thousand years, we might understand what it takes to survive in the most competitive arena on earth.

ON THE SIXTH NIGHT
of a solo Atlantic crossing, Steve Callahan had just prepared a pot of coffee and was lying on his bunk, wearing only a T-shirt, when his 21-foot sailboat collided with a whale. Thirty seconds later he was waist-deep in water, as a torrential flow poured into his cabin. In total darkness, fighting back panic, he tried to cut away the ropes that held his emergency supplies, but the cabin filled too rapidly and he was suddenly submerged. Holding his breath, he made a few desperate, futile slashes at the ropes before running out of oxygen. He forced his way up to the top of the cabin, pushed open the hatch, and got to the deck, which was awash with ocean. Callahan somehow managed to free the life raft and inflate it. Making sure it was still tethered to the boat, he shoved the raft off and dove into it.

Shivering in the raft, Callahan had his first chance to think. Every one of his actions so far, from jumping out of the bunk to diving into the raft, had been initiated by a survival instinct honed by years of sailing experience. Now he had to make his first conscious decision. He had escaped, but without his emergency bag. He knew he would not survive long on the supplies in the raft. The boat was still afloat, though bobbing below the surface whenever a wave passed over it. It could sink at any moment, taking with it those vital extra supplies. Cool judgment helped control the burst of energy produced by fear. He decided to take the chance. He climbed back aboard the boat, “feeling,” he later said, “a strange sensation of being in the sea and on
deck at the same time.” He dove through the hatch into the flooded compartment and groped in the dark for his emergency bag. The hatch above him slammed shut.

Twenty-five-year-old Lucien Schlitz and nineteen-year-old Catherine Plessz were sailing the Mediterranean on an idyllic voyage bound for the tropics. Caught in a sudden storm, their boat was tipped over by a giant wave, flooding the lower compartments. The boat righted itself and, though low in the water, continued to float. Schlitz and Plessz were not experienced sailors. They decided to try to ride out the storm in their 6-foot life raft, even though their well-provisioned 21-foot steel cutter showed no further signs of sinking. After throwing in a few meager provisions, they jumped into the raft, still tethered to the sailboat, and pushed off. Riding the waves for over two hours, they did nothing further to help themselves; they didn’t even tie in their supplies. The tethering rope snapped, and soon they drifted out of reach of their sailboat. The storm still raged; the waves grew more and more menacing. Their raft capsized and they were tossed into the sea.

Only very light winds pushed the
Albatross
as it headed from Mexico to the Bahamas, having already traveled 10,000 miles in eight months. The 92-foot square-rigged sailboat was a self-contained school ship, offering a year of combination high school and high adventure for sixteen teenage boys and their five teachers. Most were below deck one morning when they heard a sudden roar. The boat had been struck by a wind shear, a violent downdraft that strikes without warning and has been known to crash planes into runways. The slap of wind heeled the boat way over, throwing books, plates, and equipment all over the floor. The students lined up to climb the ladders to the deck, thinking more about the mess they’d have to clean up than about any imminent danger. But the boat continued to roll over. The students who had made it topside slid off the deck, spilling into the water.

________

Someone suddenly thrust into a cold, turbulent sea has no time to prepare himself mentally or physically. His first objective is to avoid drowning. However, confusion and fear will be his first reactions. Fear automatically stimulates the production of energy. How that energy is used depends on the conscious process of sorting out the confusion, transforming the flood of sensory input into a coherent status report that can be presented to the brain’s higher reasoning centers. With experience and discipline, the energy generated by fear can be channeled into purposeful action. Without it, energy will explode into panic and then dissipate into useless or even counterproductive activity.

It is ironic that the sea has become so terrifying and alien to humans. It was from the sea that all life arose. That was a long time ago, however. Most terrestrial animals have long since lost their ability to breathe water. Once submerged, the average human has less than two minutes to get his nose or mouth back into the air to survive. The body’s natural buoyancy will keep only the top of the head above water (the “dead man’s float”). But when you’re drowning, it’s hard to keep your mouth shut: sudden and unexpected contact with cold ocean water stimulates a deep reflexive gasp that forces open the mouth while still below the surface. You need to move to get your face out of the water. Driven by fear, however, such efforts induce hyperventilation—quick, short breaths that stoke the body’s metabolic fire in order to speed up energy production. The longer and harder you struggle, the more the urge to breathe intensifies, and, as with the reflexive gasp, this can open your mouth at the wrong time.

Even if you are able to exercise the discipline needed to hold your breath while struggling below the surface, you will soon enough run out of oxygen reserves. Higher brain functions will be the first affected. Oxygen flowing to your cerebral cortex will diminish, and since that is the origin of voluntary control, you will literally lose your willpower. This is why you cannot commit suicide by holding your breath, no matter how much you might want to. The drive to breathe is so primal that when no longer suppressed by fading signals from above, it resumes its automated functioning—inhaling regardless of the consequences.

Sooner or later a struggling swimmer will start taking mistimed
breaths and take water into his mouth. Water that is not spit out has but two places to go—down the esophagus (throat) to the stomach or down the trachea (windpipe) to the lungs. The stomach is used to receiving swallowed water. When it starts to hold too large a quantity, however, it becomes distended, pressing against the lungs just above it. The lungs are already having a tough time taking in air; the last thing they need is compression from below, preventing them from fully expanding.

The stomach does have a defense mechanism to counteract distension: vomiting. While drowning might not be the right time for the stomach to deal with its irritation, vomiting is another reflex over which we have no control, and it worsens matters by forcing more liquid and solid into the mouth. Seawater and stomach contents that are not spit back out or swallowed have only one other place to go—down the trachea and into the lungs. The trachea has muscles at the opening that contract into a watertight closure when they sense a solid or liquid. That protective function is called the gag reflex, and it’s what prevents food from “going down the wrong way.” That’s why it’s a good idea not to eat and talk at the same time. That’s also why it’s not a good idea to have seawater in your mouth and breathe at the same time. A drowning swimmer, however, has no choice. The trachea opens for air and gets water instead. Maybe also some vomit. All this spills down toward the air passages. Like the stomach, the lungs have a secondary defense. Reacting to the invasion, they propel their reserve air supply upward to try to blow the stuff back out: the reflex of coughing. Coughing may be lifesaving on land. In the sea, it forces open the mouth, allowing even more water to enter.

Lungs are not gills; they are collections of thousands of membranous air sacs—tiny balloons that get pumped full of air with each breath. As the air comes in contact with the lining of these sacs, oxygen is extracted and drawn through the membrane onto its outer surface. Each sac sits in a net of blood vessels that absorb the oxygen and load it into red blood cells that travel through the bloodstream like ore carts through a mining tunnel. The cells make a round-trip through the body, distributing their oxygen supply to the various organs along their route. At the same time, they collect carbon dioxide—the principal
pollutant created by the body’s machinery. When the red cells get back to the lungs, they refill with oxygen and at the same time off-load the carbon dioxide, which is expelled with the next exhalation.

The body’s appetite for oxygen is voracious. Survival depends upon maintaining a high-speed, high-volume interchange between oxygen and carbon dioxide. Oxygen supply remains the weakest link in our support system, and yet surprisingly the alarm that warns of danger is not a low-oxygen detector. The overwhelming need to breathe that we feel after roughly a minute of holding our breath is generated by sensors that monitor carbon dioxide buildup, much as a canary in a mine shaft warns of poison gas accumulation; the canary stops singing when noxious gas levels rise. The body’s sensors sing louder, on the other hand, sending electrical impulses into the hypothalamus, the part of the brain responsible for pacing respiratory muscles. The signal becomes more and more urgent as the carbon dioxide level rises.

Groping around in the dark of his submerged cabin, Steve Callahan was rapidly accumulating carbon dioxide and receiving urgent signals to breathe. With conscious effort, however, he was able to override the impulses that would have automatically restarted his breathing—and drowned him. He was able, temporarily at least, to dampen the signal by generating a countercurrent originating in his frontal cortex, the seat of his will. During that minute or so between the alarm going off and the start of brain cell death—known as the lucid interval—purposeful movement remains possible. Callahan managed to find and cut loose his emergency equipment bag, then, encountering the shut cabin hatch above him, was able to force it open. Finally, gasping for breath, he reached the surface. Later that night he watched from his raft as his sloop rolled onto its side and disappeared beneath the waves. He no longer had a boat, but he had his emergency bag. Productive use of his lucid interval would save his life.

Lucien Schlitz and Catherine Plessz were also trying to stay alive. Only a few hours earlier they had been dreaming of the tropics; now they were two bodies in an alien environment. Since the capsizing was
not a complete surprise, and the waters of the Mediterranean are not especially cold, they had avoided the gag reflex that would instantly have drowned them. Once past that danger, humans underwater will automatically hold their breath, an instinctive reaction. How deep-seated it is I demonstrated to myself the first time I put on scuba gear. As soon as I submerged, I stopped getting any air, so I surfaced and switched tanks. My second rig proved no better. When I explained the problem to my instructor, he told me that the blockage was not in the hose; it was in my head. What was preventing me from breathing was instinct.

Their life jackets kept Schlitz and Plessz’s heads above the surface, and due to instinct, they hadn’t yet swallowed any water. Pounded and pummeled by heaving waves, they held on to their overturned yet still buoyant raft. With waves washing over them continuously, their air intake contained large quantities of water, but being conscious, they were able to cough back up any water that entered their lungs through mistimed breaths. Preprogrammed automated survival defenses, and technology, were keeping them alive. So far.

Between waves, they somehow managed to right the raft and climb inside. Their supplies, which they had neglected to tie down, had been washed overboard. Under relentless attack from wind and waves, the raft flipped over again. Once more they were able to turn it right side up and get back inside. The wild ride continued all night, tossing them into the sea a third time. Again they struggled back on board. This time they held on until morning. Huddled in their empty raft, with no food or water, they looked out at the now calm sea, powerless to regain their well-provisioned and still floating sailboat, which had disappeared over the horizon.

Also still afloat was the
Albatross.
Though it had been pushed onto its side by a sudden wind shear, it was still within reach of the students who had slid off its deck. They were relieved to see the boat right itself. Then, horrified, they watched it sink rapidly. Its lower compartments had been flooded. Some of their classmates and teachers were still inside.

A lungful of air will provide at most about two minutes of consciousness. Frantic activity and fear will burn it up a lot quicker. Even
two minutes is not enough time to work your way out of the maze of underwater passages in a 92-foot sailboat plummeting to the bottom of the ocean. As the air supply runs out, the metabolic fire dims, and like any fire burning without enough oxygen, by-products build up. Chemical reactions in every organ are disrupted. The brain, critically dependent on a steady supply of oxygen, is affected first. It selectively protects the lower, more primitive centers, the ones that maintain heartbeat and breathing, at the expense of the higher, less immediately critical centers such as the ones that control reasoning and will. Blood containing what little oxygen is left is shunted to the hypothalamus and away from the frontal cortex, in a desperate attempt to maintain basic life functions. The chemistry and electricity of the frontal cortex begin to go awry. Confusion and panic overtake reasoning, and willpower cannot be generated. The insistent signal to breathe goes unchecked. The mouth opens. Seawater rushes in, and what is not swallowed runs down the trachea into the lungs. The mechanics of breathing is violently disrupted. Air sacs fill like water balloons. Oxygen cannot be extracted, and carbon dioxide cannot escape.