Human vs cetacean divers

Essay by chuck laiCollege, UndergraduateA+, December 1996

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Following a deep dive in water, humans can experience severe pains upon returning to the surface too quickly, and the resulting

body injury may cause unconsciousness and death. Aches are so severe in some cases, commonly in the joints, that divers

bend over in agony. Hence, the name, the bends. However, the more common name for this condition is decompression

sickness, meaning that the sickness results from decreasing pressure.

Divers experience decreasing pressure upon ascent to the surface of the water. This is expected because pressure gradually

increases with increasing depth of the water. Increases in pressure with depth are a result of increasing weight of the water. For

example, at 150 feet, because of this weight, pressures on all surfaces of the body are four and one-half times greater than they

are at the surface. At this depth, pressure on the diver's chest cavity, lungs, and air within the lungs causes gases such as

nitrogen in that air to dissolve in the blood of lung tissue.

Dissolved nitrogen at high pressure and deep water causes no

problems as long as the diver does not ascend. When the diver ascends, pressure decreases (decompression), and nitrogen is

released from the blood into body tissues as bubbles. This process is similar to the appearance of bubbles in a soda after the

cap is removed. Bubbles appear because the pressure that kept them dissolved was removed with release of the cap. These

nitrogen bubbles in tissues are the factor which cause damage, sickness, and death. However, some mammals do not

experience decompression sickness. These are the whales, porpoises, and dolphins, known collectively as cetaceans.

Cetaceans do not experience complications during dives as humans do, even though nitrogen dissolves in the blood of

cetaceans to the depth of 200 feet. Beyond that level, cetacean...