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Snorkeling Elephants and the Secrets of Breathing |
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Hillary Mayell for National Geographic News |
| November 6, 2002 |
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What do snorkeling elephants, astronomers, Himalaya mountain climbers, and miners in Chile have in common? They all have unusual breathing requirements, and at some point John B. West, a pulmonary physiologist at the University of California–San Diego School of Medicine, has studied them all. For West, it's all about lungs. You might figure that a guy with a string of letters behind his name—Ph.D, M.D., D.Sc.—and a job description like "pulmonary physiologist" would be in contention for most boring guy on planet Earth. You would be wrong. West could be the poster boy for a Science is Fun campaign, and when you look at what he's done, you'd be absolutely convinced: Science is enthralling. Early in his career, West traveled to the Himalaya with Sir Edmond Hillary on the 1960-61 Silver Hut Expedition. He and a group of scientists lived for five months just south of Everest at an elevation of 19,000 feet (5,800 meters) as part of an experiment to discover the effects of long-term oxygen deprivation on the human body. Twenty years later, he returned to Mount Everest as leader of the American Medical Research Expedition. "We had a lab quite high on Everest at nearly 21,000 feet (6,300 meters). From there, three younger climbing scientists with two sherpas went to the top," he said. The team took the first physiological measurements ever made at 29,028 feet (8,848 meters). His most recent passion? Working to answer a 300-year-old mystery of why elephants have such a peculiar lung structure. Unusual Lungs More than 2,300 years ago, Aristotle wrote about elephants crossing rivers and lakes completely submerged, with only the tips of their trunks above the water, like built-in snorkel tubes. From a physiological point of view, this should be impossible; the differences in pressure exerted by the outside air and the deep water should cause the blood vessels in the lining of the lungs to burst. "That's why you can't buy a snorkel more than 30 centimeters long (12 inches)," said West. In 1681, a scientist in Dublin, Ireland, conducted an autopsy on an elephant that had died in a fire and wrote that the elephant's lungs were different from those of any other four-legged animal he'd ever seen. Since then, the big question has been why. Does it have anything to do with the elephant's snorkeling ability, and is it the result of evolution? In all other mammals, the lungs are surrounded by two layers of a thin membrane called the pleural cavity. Imagine a double-bagged garbage can: The can is the ribs, the trash is the lung, and the space between the two bags is the pleural cavity. In humans and other mammals, there's about a teaspoon of liquid between the two layers. In elephants, the pleural cavity is filled with connective tissue. "It's not muscle and it's not meat—it's slippery-slidey kind of stuff that allows bits to slide over each other," said West. "No other mammal," he pointed out, "has that anatomy." The unusual lung structure enables elephants to withstand the extreme differences in pressure above and below water without rupturing blood vessels in the lining of the lungs. Genetic evidence suggests that the elephant's closest relatives in evolutionary terms are manatees and dugongs, herbivorous sea cows that live full-time in the water. For some reason—the availability of a food source that no other creature was exploiting is one possibility—elephants, over time, developed legs that were strong enough to support their huge body weight and enabled them to become land creatures. West suggests that elephants also evolved trunks so they could breathe with their heads underwater. To this day, elephants remain powerful swimmers. Astronomers, Climbers, and Miners What about mountain climbers in the Himalaya, astronomers, and miners in Chile? They all work at high altitudes, breathing "skinny" air. At sea level, air contains about 21 percent oxygen. The pressure decreases as altitude increases; at 12,000 feet (3,658 meters) there are roughly 40 percent fewer oxygen molecules per breath. To deal with the lower oxygen content, people at high altitudes start breathing much faster, even while resting. One climber likens it to running on a treadmill while breathing through a straw. Breathing thinner air has lots of potential consequences, none of them good. Symptoms range from headache, loss of appetite, and insomnia to delusional thinking, loss of coordination, and life-threatening medical conditions known as high-altitude pulmonary edema and high-altitude cerebral edema. "We're working on developing a new technique of oxygen enrichment of room air to allow people to work in conditions where otherwise they'd be hopelessly inefficient," said West. "Really it's for commuters from sea level to high altitudes, like astronomers, who have to be as high up in the world as they can get," he explained. The technique could also prove useful at ski resorts. "There is one resort in Cuzco, Peru, which is a little over 11,000 feet, where they're using it," said West. "The problem with Cuzco is that everybody comes in straight from sea level. They fly in from Lima, and they're immediately at this quite high altitude, and they have a lot of problems with it." For West, there is no end to the fascinating things a scientist can discover. "The excitement of science," he said, "is that if you're curious, there are very interesting things you can unearth." 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