Scuba diving and compressed air injuries

In the United States, there are over 1,000 diving-related injuries each year, of which >10% are fatal. Similar injuries can occur to workers in tunnels or caissons, which use compressed air to remove water from work areas. Many injuries are related to the high pressures that are created at depth or in caissons by the weight of the water column plus the atmospheric pressure at the surface. At a depth of 10 m (33 ft), seawater creates a pressure equal to standard atmospheric pressure at sea level, which is 14.7 psi, 760 mm Hg, or 1 atm (absolute atmosphere). Thus, the total pressure at this depth is 2 atm. For every additional 33 ft of depth, there is an additional 1 atm.

The volume of gases in body cavities is inversely proportional to the external pressure. An increase or decrease in gas volume due to a change in pressure outside the body has a direct physical effect that can damage various body tissues (barotrauma). The amount of gas dissolved in the bloodstream increases with increasing ambient pressure. Increased gas content can cause both direct (e.g., nitrogen narcosis, O2 intoxication) and indirect injuries during ascent from depth when decompression of the gas-saturated bloodstream causes nitrogen bubble formation (the bends). Barotrauma or decompression can cause arterial gas embolism. Information on other diving-related injuries (e.g., drowning, hypothermia, trauma) is provided in the relevant sections of the manual.

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