High Tech For The Deep

Back in the days of the TV show Sea Hunt, Mike Nelson's biggest concern was running out of air. Today scuba divers wonder whether they should even be breathing the stuff. Some of them aren't.

The last time Ed Soellner went diving, he chose to breathe something other than air—something he hoped would ensure against decompression illness, or the crippling malady called the bends. But instead of being "bent," he wound up dead.

Soellner drowned on July 5, 1992, apparently after suffering a seizure while he was exploring a shipwreck off the New Jersey coast. The convulsion was most likely caused by the high oxygen content of the gas he was breathing—a blend called enriched air, or nitrox. Soellner, an accomplished diver who was 33 when he died, was one of four who lost their lives in 1992 while breathing gases other than air.

Underwater, ordinary compressed air has a number of disadvantages—including a contributing role in the bends. Under pressure, a diver's body absorbs nitrogen from the gas in his or her tank. This is usually harmless, but under certain circumstances the nitrogen can form bubbles in the body as the diver ascends. If these bubbles lodge in the joints and elsewhere, they wreak havoc with nerve function and blood flow.

Another problem with nitrogen is its tendency to cause narcosis, a.k.a. "rapture of the deep," an effect that is the equivalent to standing up quickly after drinking a pitcher of margaritas. A diver suffering from narcosis may become disoriented and fail to keep track of his air supply or the location of his dive boat.

Seven or eight years ago a handful of scuba divers began diluting the air in their tanks with additional oxygen, assuming that less nitrogen in one's mix would mean safer dives. The idea wasn't new—commercial and military divers had been using enriched air for years—but it was an innovation for people who weren't being paid to dive. Enriched air does offer some advantages. It can give a diver more time on the bottom or lessen the chances of decompression problems, and it may be particularly useful for older divers, who seem to be more prone to the bends.

"Any time I'm diving shallower than 130 feet, I use enriched air," says Evelyn Bartram Dudas, 48, of West Chester, Pa. She became certified in its use in 1991. A veteran diver, Dudas was paralyzed temporarily in 1968 following an air dive to 165 feet. Until she started using enriched air, she suffered skin bends, which can appear as a rash or blotches, "about every third day of diving."

"I'm not sure that it will replace air, but it certainly has a place in recreational diving," says Joe Clark, 53, a co-owner of Ocean Divers in Key Largo, Fla. In 1988 Clark became the first dive operator to offer enriched air to recreational divers. "It's good for people my age who like to dive a lot. If you don't use it to stay down longer, you have a built-in safety factor."

The trade-off is the potential for oxygen toxicity. Oxygen is vital to life, but in high concentrations it becomes a poison, causing nausea, vision problems, irritability, even convulsions. Furthermore, an individual's reaction will vary depending on the length of time spent underwater, one's depth, the percentage of oxygen in the mix and one's body chemistry on a given day.

An analysis of the gas Soellner was breathing when he died showed it had a higher percentage of oxygen than experts would recommend for the depth and duration of a dive such as his. Proponents of enriched air say they were saddened but not surprised by Soellner's death.