Decompression Syndromes: The Bends (cont.)
IN THIS ARTICLE
The Bends Causes
Nitrogen or any gas from a diver's air tank increases in pressure as a diver descends. For every 33 feet in ocean water, the pressure due to nitrogen goes up another 11.6 pounds per square inch,. As the pressure due to nitrogen increases, more nitrogen dissolves into the tissues. The longer a diver remains at depth, the more nitrogen dissolves. Unlike the oxygen in the air tank a diver uses to swim underwater, the nitrogen gas is not utilized by the body and builds up over time in body tissues. The underlying cause of symptoms throughout the body is due mainly to nitrogen bubbles being released when the diver returns to sea level and blocking blood flow and disrupting blood vessels and nerves by stretching or tearing them. They may also cause emboli, blood coagulation and the release of vasoactive compounds.
A clear example to illustrate this bubble formation process is that of a bottle of carbonated soda. A bottle of carbonated soda is filled with gas (carbon dioxide), which cannot be seen because it is dissolved in solution under pressure. When the bottle is opened, the pressure is released and the gas leaves the solution in the form of bubbles. A diver returning to the surface is similar to opening the bottle of soda. As a diver swims to the surface, the pressure decreases. The nitrogen, which has dissolved in tissues, wants again to leave, because the body can hold only a certain amount based on that nitrogen pressure.
Medically Reviewed by a Doctor on 3/17/2015
Scott D. Fell, DO, FAAEM
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Although decompression sickness (DCS), a complex resulting from changed barometric pressure, includes high-altitude–related and aerospace-related events, this article focuses on decompression associated with the sudden decrease in pressures during underwater ascent, usually occurring during free or assisted dives.