More than 1000 diving-related injuries occur annually in the US; > 10% are fatal. Similar injuries can befall workers in tunnels or caissons (watertight retaining structures used for construction), in which pressurized air is used to exclude water from work sites.
Many injuries are related to high pressure, which, at depth or in a caisson, results from the water weight above plus the atmospheric pressure at the surface. At a depth of 10 m (33 ft), seawater exerts a pressure equivalent to standard sea level atmospheric pressure, which is 1.03 kg/sq cm (14.7 lb/sq in), 760 mm Hg, or 1 atmosphere absolute (atm abs); thus, the total pressure at that depth is 2 atm abs. Every additional 10 m of descent adds 1 atm.
The volume of gases in body compartments is inversely related to external pressure; an increase or a decrease in gas volume due to pressure change exerts direct physical forces that can disrupt various body tissues (barotrauma Overview of Barotrauma Barotrauma is tissue injury caused by a pressure-related change in body compartment gas volume in air-containing areas. During ascent, gas expansion affects the lungs and gastrointestinal (GI)... read more ). The amount of gas dissolved in the bloodstream increases as ambient pressure increases. Increased gas content can cause injury directly (eg, nitrogen narcosis Nitrogen narcosis Various physiologic (eg, oxygen, nitrogen, carbon dioxide) and nonphysiologic (eg, carbon monoxide) gases can cause symptoms during diving. (See also Overview of Diving Injuries.) Oxygen toxicity... read more , oxygen toxicity Oxygen toxicity Various physiologic (eg, oxygen, nitrogen, carbon dioxide) and nonphysiologic (eg, carbon monoxide) gases can cause symptoms during diving. (See also Overview of Diving Injuries.) Oxygen toxicity... read more ) or indirectly during ascent when decompression of the supersaturated blood or tissues releases nitrogen bubbles (decompression sickness Decompression Sickness Decompression sickness occurs when rapid pressure reduction (eg, during ascent from a dive, exit from a caisson or hyperbaric chamber, or ascent to altitude) causes gas previously dissolved... read more ). Arterial gas embolism Arterial Gas Embolism Arterial gas embolism is a potentially catastrophic event that occurs when gas bubbles enter or form in the arterial vasculature and occlude blood flow, causing organ ischemia. Arterial gas... read more can result from barotrauma or decompression.
Some medical disorders, if they cause symptoms at depth, may be disabling or disorienting and thus lead to drowning (see table Specific Medical Contraindications to Diving Specific Medical Contraindications to Diving Diving is a relatively safe recreational activity for healthy people who have been appropriately trained and educated. Diving safety courses offered by national diving organizations are widely... read more ).
For other diving-related injuries (eg, drowning Drowning Drowning is respiratory impairment resulting from submersion in a liquid medium. It can be nonfatal (previously called near drowning) or fatal. Drowning results in hypoxia, which can damage... read more , hypothermia Hypothermia Hypothermia is a core body temperature 35° C. Symptoms progress from shivering and lethargy to confusion, coma, and death. Mild hypothermia requires a warm environment and insulating blankets... read more , trauma Traumatic Brain Injury (TBI) Traumatic brain injury (TBI) is physical injury to brain tissue that temporarily or permanently impairs brain function. Diagnosis is suspected clinically and confirmed by imaging (primarily... read more ), see elsewhere in THE MANUAL.
Physicians caring for patients with diving or compressed air injuries may contact the Divers Alert Network: 919-684-9111 for emergencies and 919-684-2948 for other information. Physician-to-physician consultation can be obtained through Duke Dive Medicine: 919-684-8111.