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."

Lethal Oxygen. Most types of scuba are of open-circuit design which supply air on demand, and discharge exhaled air into the water--so carbon dioxide presents no problem. Dr. Lanphier has little use for closed-circuit, rebreathing types which need a carbon dioxide absorbent: "The average sport diver dives only added limitations and hazards from using [them]."

The greatest dangers to a skillful diver obeying all the rules at unusual depths come only indirectly from pressure. They have to do with the altered behavior of the gases in the air he breathes. Oxygen, which is vital to life, becomes poisonous under the pressure encountered at 280 ft. The supersaturation of oxygen in the blood then attacks the central nervous system, causing convulsions indistinguishable from those of grand-mal epilepsy or electroshock treatment. A diver may drown as a result. If he is more fortunate, he will have warning symptoms such as localized muscular twitching, nausea or giddiness; he may still keep his wits about him sufficiently to make a controlled ascent. He may be depressed or unconscious, restless and irrational for a while, but can expect a full recovery with no serious aftereffects.

More hazardous than oxygen is nitrogen. Even at the 100-ft. depth, most divers have their thought and judgment so impaired by nitrogen narcosis that they can no longer perform simple mental or manual tasks well. As he descends, the diver falls victim to partial anesthesia and reaches a state which Pioneer Skindiver Jacques-Yves Cousteau has called the "rapture of the deep." In most cases he becomes giddy and laughs uproariously; some divers in this euphoric state have been tempted to rip off their masks and offer them to passing fish; a few divers become taciturn and others tearful. Dr. Lanphier is strictly matter of fact: "At about 250 ft., the average diver has lost most of his usefulness and has become a menace to himself."

The greatest danger is that, by its very nature, this euphoria keeps a diver from recognizing a hazardous situation and taking effective action. At best, he is likely to stay down too long and then try to come up too fast. This makes him a candidate for the most feared of all diving diseases, "the bends"--or as Dr. Lanphier prefers, "decompression sickness."

Bubble Trouble. At ordinary atmospheric pressure, small amounts of the gases in the air are dissolved in the blood. At greater pressures, more gas goes into solution. During an ascent, it must come out of solution. Oxygen does so readily and harmlessly; nitrogen forms bubbles which collect in the joints and press against nerves, causing great pain, and threatening life itself by blocking blood vessels in the brain. There is only one remedy, says Dr. Lanphier, if a diver has stayed down too long or risen too fast and got the bends: put him back under pressure, so as to force the nitrogen into solution again, and then decompress him very slowly to let the gas work out gradually. A professional diver in a suit and helmet with air lines can simply be dropped back over the side to do this, but not a skindiver with only the air that he carries in the cylinders on his back. He must go into a recompression chamber.

Lanphier prefers prevention to cure: by Navy standards, skindivers should not spend more than two hours under water at 40 ft., not more than 30 min. at 90 ft., and not more than 15 min. at 130 ft. The rate of ascent should not exceed 60 ft. a minute.

Some people, Dr. Lanphier believes, should not even think of becoming skindivers : those with heart trouble or breathing difficulties, the obese, those who cannot easily equalize the pressure in their middle ear and sinuses, those with a perforated ear drum, and the reckless. Also, "men over 40 deserve special scrutiny." But the Navy expert's outlook, for all his warnings, is far from negative. Many physicians, notes 34-year-old Dr. Lanphier, a skindiver himself, regard diving as "a sport worthy of their own leisure moments. A more fascinating activity or a better means of keeping in condition is not easy to find."

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