Medicine: Scuba Hazards

Man, designed by nature to plod the surface of the earth and occasionally to flounder in the uppermost layer of its waterways, gets into trouble when he tries to go either up or down. The medical hazards of high-altitude flying have long been studied. Until recently, the corresponding dangers of the deep have been the private preserve of Navy "diving doctors" working with submariners and deep-sea divers. Now, with the craze for skindiving, with Aqua-Lungs, snorkels and similar gadgets sold in the corner store, civilian doctors are daily confronted with unfamiliar problems. In the New England Journal of Medicine, one of the Navy's top underwater medicinemen, Lieut. Edward H. Lanphier, offers a primer. Dr. Lanphier, of the Navy's Experimental Diving Unit in Washington, D.C., is principally concerned about amateurs who use "scuba"—the skindiver's abbreviation for self-contained underwater breathing apparatus.

Body & Bucket. The most obvious change in the environment as a man dives deeper is the increase in pressure: equivalent to a whole atmosphere (15 lb. per sq. in.) for every 33 ft. of salt water (34 ft. of fresh water) through which he descends. Much nonsense has been written about this "tremendous crushing force," Dr. Lanphier notes, but "the body as a whole, being made up of solids and fluids, is no more likely to be crushed than a bucket of water lowered into the depths." Damage can occur only when there is an unequalized difference of pressure—and that means where there is air, i.e., in the lungs and airways, paranasal sinuses and the middle ear. (Gas in the gut gives no trouble because the supple intestinal walls simply contract to equalize the pressure.)

So long as a diver is breathing normally and has an ample supply of air, his lungs and airways will easily establish a pressure equal to that of the water at his depth. But if he holds his breath while descending, he creates a low-pressure pocket in his lungs: his blood is at a higher pressure, and blood vessels (especially in the lungs, but also in the eye socket and ears) may burst. This will cause the spitting of frothy blood—an alarming symptom, but in this case not likely to be fatal.

A diver who holds his breath while ascending is in a far worse plight: instead of a low-pressure pocket, a high-pressure pocket forms in his lungs, which may burst as a result. The diver is, says Dr. Lanphier, "immediately a candidate for one of the most serious of all diving accidents: air embolism." Apart from the danger of a lung bursting, the abnormal pressure can force air bubbles through the pulmonary veins and into the heart. The bubbles usually travel to the brain, causing convulsions and unconsciousness, and unless the victim is treated promptly by recompression, he is almost certain to die. The greatest danger of air embolism is in emergency ascents—perhaps after the scuba has gone out of kilter at great depth. Dr. Lanphier notes: "Only a well-instructed and coolheaded diver can be expected to repress the powerful instinct to hold his breath on making his way to the surface. Air embolism is believed to be second only to drowning as a cause of death in sport diving, but it is often unrecognized."