High Hazard

Airmen, their heads higher & higher in the skies, got a word of warning last week. Dr. Samuel Gelfan of the Yale University School of Medicine explained that the pressurized cabin, which has solved many of the problems of high-altitude flying, has in turn created a new and equally tough problem: explosive decompression. The trouble can be caused either by a leak in the tightly sealed cabin or by a sudden failure of the pressurizing equipment.

Passengers aboard a pressurized, transatlantic Constellation last year knew what Dr. Gelfan meant: at 19,000 feet, the astrodome had blown off, and with the release of the inside pressure the navigator had been shot out after it. Had the plane not been brought down quickly to a lower altitude, the passengers would soon have felt wobbly, slightly drunk, and would have lost consciousness in a few minutes. At 20,000 feet the pressure can be restored merely by diving, but at 40,000 feet an oxygen mask is needed. Above 52,000 feet, a new problem comes up.

By experimenting with monkeys in specially constructed pressure chambers, Dr. Gelfan, an assistant professor of physiology, has learned that at 52,000 feet the barometric pressure of the air is so low that it is about equal to the pressure inside the tiny blood vessels of the lungs. Under such conditions, there is not enough pressure to force the oxygen through the walls of the blood vessels and into the bloodstream. Explained Dr. Gelfan: "At the moment of decompression . . . the pressure of oxygen in the blood would be greater than in the lungs, and under such circumstances oxygen is actually lost by the blood to the lungs."

Decompression at such altitudes is in itself not fatal (monkeys have withstood it at 75,000 feet), provided the victim is returned almost immediately to a lower altitude. But humans black out in about 15 seconds, too little time for a pilot to descend to a tolerable altitude.

Dr. Gelfan concludes that the hazard of explosive decompression puts an altitude limit on planes. The limit can be raised only by structural improvements in the pressurized cabins or by some such safety device as automatic, delayed-action parachutes.

This file is automatically generated by a robot program, so reader's discretion is required.