Military Medicine

What is 'the bends'?

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2012-05-23 02:45:45

Nitrogen 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 for any specific depth. Nitrogen gas is not utilized by

the body and builds up over time in body tissues. If a diver

surfaces too fast, the excess nitrogen will come out rapidly as gas

bubbles. Depending on which organs are involved, these bubbles

produce the symptoms of decompression sickness. The process is

similar to shaking a can of carbonated soda. If the pressure is

high enough, the carbon dioxide in the soft drink will emerge out

opening of the can as a gush of bubbles. The bends are joint pains

involving the arms or legs. Intensity varies from mild to severe.

Arms are more commonly involved than legs. The pain is most

prominent around joints and in the upper shoulder area. It is

sometimes relieved by direct pressure. This occurs because nitrogen

is released into the joints and muscles.


A small change is that the pressure inside a suba cylinder does

not change depending upon depth as it is nonflexible container.

However, the parital pressures of the gases breathed due change

once they exit the cylinder (i.e. are breathed).

DCS is caused from the gas a diver absorbs during a dive coming

out of solution in a divers tissue and thus bubbling. These bubbles

push on nerves in the body causing pain as well as an injury. The

two common types of DCS are know as Type I (pain only bends) and

Type II (central nervious system bends). It is likely a diver will

develop both. DCS is occurs due to excessive gas in the body

bubbling and exceeding the bodies capacity to deal with the


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