Extreme Medicine Read Free

winds are a manifestation of inequalities in pressure and the system’s natural tendency to smooth those differences out. In the same way that this difference allows turbines to harvest energy from wind, the body can exploit the flow of ions across cell membranes.
    The flow of ions, along with the beautifully elegant machinery that exploits it, makes complex life possible. It keeps the whole that is greater than the sum of its parts—the whole that is ultimately Scott—going.
    It has taken me most of my medical career to finally appreciate the tiny processes that enable biological systems to store and release energy. These biochemical events individually appear to bear little relation to the wonder of life, when in fact collectively they
are
life; they are everything we do, everything we are.
    The privilege of the human body’s complexity is bought at a price: It must expend energy pumping ions where they don’t want to be in order to keep the body going. When that price is no longer affordable, simplicity reigns once again. And here simplicity is synonymous with death.
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    T HE ENVIRONMENT OUTSIDE the tent abhors Scott’s complexity. There is more at work here than temperatures that can freeze exposed flesh in seconds. First, there is Antarctica’s aridity. The continent’s great sheets of ice hold water locked away, and less than a single inch of rain falls there each year. So the Ross Ice Shelf is considered a desert, and it will attempt to dehydrate and desiccate Scott’s body. With much of the continent thrust two miles above sea level, Scott is high enough to make heavy exertion uncomfortable, even for the acclimatized. That’s not to mention the scouring Antarctic winds, which will carry heat away from his body, driving his temperature down. All told, Antarctica is a continent of fierce extremes: the coldest, the highest, the most parched. Its climate has made it uninhabitable for all but the last hundred years of human history.
    Bleak though Antarctica may be, it’s important to consider how Scott’s body reacts to his plummeting temperature, because that process is the key to an extraordinary advance in future medical technology.
    As Scott’s core temperature drops, the pumps that move ions across his cell membranes are grinding slowly but surely to a halt. The process is inexorable. In the absence of energy, borrowed from the fuel of food and burned in the fire of the oxygen that we breathe, the pumps wind down and eventually stop. The ions begin to assume equal concentrations on either side of the cell membranes. This simple symmetry is how death begins.
    Scott isn’t yet ready to die. His physiology, ignorant of his predicament, is designed to battle for him, to buy him every moment that it can, to give him his best chance of survival. As Scott writes, he feels the heat draining out of his hand. The blood vessels that run in his body’s periphery, carrying hot blood to his skin’s surface and losing that heat uselessly to the outside world, are constricting. His body hair stands on end in an effort to trap more air close to his skin. Both of these measures are an effort to reduce conductive heat losses. In the context of the Antarctic environment, however, this physiological strategy is next to useless.
    Next, Scott will begin to shiver uncontrollably, generating enough heat to slow the drop in his temperature. This shivering is more than the casual tremor we might experience at a bus stop in midwinter; Scott’s muscles will shake themselves as hard as they can, consuming fat and carbohydrates ravenously. This type of shivering, a last desperate attempt at staving off death, becomes an act of physical endurance in itself. It can account for fully 40 percent of the body’s maximum exercise capacity and it will continue while there is fuel enough to do so. But shivering, no matter how athletically, is merely a holding measure, the