Deco Drug?

Today, proper decompression requires a slow enough trip to the surface to eliminate dissolved gases. Tomorrow, it may require only a pill.

A research team at the Naval Medical Research Institute in Bethesda, Maryland, is working on a method for decompressing divers that removes some of these gases by biochemical processes, using bacterial metabolism.

The bacteria are packaged, swallowed, and delivered to the large intestine before the start of the dive. During the dive, some gas in the blood diffuses into the intestine, down the partialpressure gradient created by the metabolism of that gas by the bacteria. End products of this metabolism have a safe route for elimination from the intestine.

The researchers have been successful with laboratory rats, using hydrogen in the breathing mixture and bacteria that metabolize hydrogen and carbon dioxide to methane and water.

When the rats were pressurized in a hyperbaric chamber, the rate at which they released methane increased with increasing pressure of hydrogen in the chamber. The hydrogen breathed by the rats reached the bacteria within seconds to minutes and the conditions in the intestine were suitable for these bacteria to metabolize the hydrogen. The treatment reduced the rate of decompression sickness from 50 percent to approximately 20 percent, which we had accurately predicted.

Hydrogen diving was originally conceived in the 1940s to reduce difficulties encountered by divers breathing helium-gas mixtures at great depths. But a researcher met a tragic death during an experimental hydrogen dive in 1945, and it wasn't researched again until the 1970s. Last summer, using a trimix of hydrogen, helium, and oxygen, divers conducted successful dives to 210 meters.

While it's a leap from hydrogen to nitrogen, federal government researcher Susan R. Kayar says that it's "even more exciting that nitrogen-metabolizing bacteria can be used to achieve biochemical decompression for air dives. While still years of animal and then human research away, the possibility exists that swallowing a few capsules the night before a dive might make sport divers safer from the risk of decompression sickness."

Ben Davison