People who engage in deep-sea or scuba diving are at risk of a number of injuries. Diving in cold water can rapidly lead to hypothermia (dangerously low body temperature), which causes clumsiness and poor judgment. Cold water can also rarely trigger fatal heartbeat irregularities in people with coronary artery disease. Other potential diving hazards include
Drugs (prescribed, recreational, and some over-the-counter) and alcohol may have unanticipated, dangerous effects at depth.
Most diving-related disorders, however, are caused by changes in pressure. These disorders also can affect people who work in underwater tunnels or caissons (watertight enclosures used for construction work). Such structures contain air under high pressure to keep out water.
High pressure under water is caused by the weight of the water above, just as barometric (atmospheric) pressure on land is caused by the weight of the air above. In diving, underwater pressure is often expressed in units of depth (feet or meters) or atmospheres absolute. Pressure in atmospheres absolute includes the weight of the water, which at about 33 feet (10 meters) is 1 atmosphere (14.7 pounds per square inch [72 kilograms per square meter]), plus the atmospheric pressure at the surface, which is 1 atmosphere. So a diver at a depth of 33 feet is exposed to a total pressure of 2 atmospheres absolute, or twice the atmospheric pressure at the surface. With each additional 33 feet of depth, the pressure increases by 1 atmosphere.
Diving disorders can be divided into various categories: Some result from expansion or compression of gas-filled spaces in the body (barotrauma), and others result from release of dissolved nitrogen in the blood and tissues (decompression sickness). Either process can cause bubbles in arteries to block blood flow to organs (arterial gas embolism). Gases such as oxygen and nitrogen can also cause disorders when breathed at high pressures, such as when people dive to very deep depths.
Diving disorders can result in drowning if they cause any of the following:
Last full review/revision February 2009 by Alfred A. Bove, MD, PhD