Safe Diving for Whales

Q. Why don't whales get the bends?

A. Luckily for deep-diving whales, they have an entirely different system from that of humans for handling the air they breathe before diving and their oxygen needs while diving, said Kevin M. Walsh, director of marine mammal training at the Aquarium for Wildlife Conservation in Coney Island, Brooklyn.

The release of pressure on dissolved gases is what causes the bends. Whales are taking in air breathed at the surface and carrying it to the bottom, not breathing pressurized air underwater, Mr. Walsh said. Besides, they don't carry much with them in the first place, because they don't need it while diving.

The bends, also called decompression sickness and caisson disease, appears in divers who breathe compressed air in caissons and diving apparatuses after a rapid reduction in air pressure when they come back up. Symptoms include skin itching, joint pain and nervous system impairment. Severe cases, if untreated, can lead to partial paralysis or degeneration of bones and joints.

The symptoms result from the formation of bubbles of gas in tissues during the ascent; bubbles may block blood vessels and start a cascade of problems. Trained divers avoid the bends by allowing gas to escape slowly in a gradual ascent.