Natural Life Preservers

"Diving reflex" and chill waters can prevent drowning deaths

Doctors and lifesaving manuals have long repeated that few drowning victims are likely to survive more than four to six minutes under water. Chances are that anyone who does will have irreparable brain damage from lack of oxygen. But consider the case of Brian Cunningham, 18, of Jackson, Mich. In March 1975 Cunningham's car plunged through the ice of a frozen pond; when rescuers hauled him out 38 minutes later, his body was blue. He had no pulse, his breathing had stopped, and his eyes were fixed in a dilated, glassy stare. Cunningham, in fact, was declared dead from drowning. Then he belched. The involuntary reaction convinced rescuers that, despite all contrary evidence, they should try to revive him. A high-speed ambulance ride, two hours of cardiopulmonary resuscitation and 13 hours of breathing assistance later, Cunningham regained consciousness--and more. Far from being brain-damaged, he finished the semester at Jackson Community College with a 3.2 average.

Cunningham's story is unusual, but it is not unique. Dr. Martin Nemiroff, 36, of the University of Michigan Medical Center, has documented about a dozen similar cases, in which apparently drowned victims recovered from cold waters have been successfully revived. His amazing findings not only offer new hope to those who may share Cunningham's rare experience, but they also impose new responsibilities on the rescuers.

Nemiroff, an ardent scuba diver, began his research on a grant from the National Oceanic and Atmospheric Administration after hearing reports of people who had survived long submersion without apparent ill effect. A study of some 60 near drownings convinced him that in warmer waters, the limit for submersion without death or brain damage probably was four minutes. But in waters below 21DEG C. (70DEG F.), the four-minute rule seemed to be suspended. Of 15 victims rescued after a minimum of four minutes from the chilly waters that abound in Michigan, Nemiroff found, two died of lung infections and two suffered brain damage. But eleven, including Cunningham and a physician who has since successfully resumed his medical practice, were resuscitated without long-term injury. "The patients are as damaged as, say, somebody who is hit on the head with a blackjack. There is brain damage, but it is usually reversible in the first 24 hours."

The reason, says Nemiroff, is a combination of coldness, which lowers the body's need for oxygen, and an old mammalian response known as the diving reflex. The reflex was studied in the 1930s in diving mammals, like the porpoise and seal, which can remain submerged without breathing for periods of 20 minutes or more. And, confirms Nemiroff, the same automatic response works in humans as well. Triggered by held breath and cold water on the face, the diving reflex slows the heartbeat and the flow of blood to the skin, muscles and other tissues that are relatively resistant to damage from oxygen deprivation. At the same time, it sends the body's remaining oxygenated blood to the heart and to the brain, whose cells will indeed begin to die after about four minutes without oxygen. Bradycardia --the slowing down of heartbeat associated with the diving reflex--can even be induced by immersing the face in a bowl of cold water while holding the breath for 20 seconds or so.

In mammals, at least, the diving reflex seems to derive from the need of the fetus to survive when oxygen may be cut off during its trip down the birth canal. (When a pregnant woman holds her breath under water, sufficient oxygen is automatically shunted to her uterus to protect her baby as long as possible, just as it is to her own heart and brain.) Indeed, says Nemiroff, the reflex is stronger and more swiftly triggered in children.

The doctor's findings should prove encouraging to anyone who swims, sails or fishes in the cold waters of the North Atlantic or the icy lakes of the upper Midwest. But Nemiroff s conclusions place a greater burden on friends, lifeguards, rescue crews and physicians. At present, rescuers are likely to assume that a drowning victim with cold, blue skin, no detectable pulse or heartbeat, and fixed, dilated pupils is dead, and they may not quickly begin, or may at least too soon abandon, any effort to revive him. In fact, efforts to resuscitate should not only be started immediately, but should be kept up until it is clear that they are fruitless.

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