- Also called:
- bends or caisson disease
- Key People:
- Paul Bert
- Related Topics:
- barotrauma
- taravana syndrome
- diversā itch
- diversā palsy
- diversā stagger
- On the Web:
- National Center for Biotechnology Information - Scuba Diving Physiology (Nov. 07, 2026)
decompression sickness
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What is decompression sickness?
Decompression sickness is a potentially fatal condition caused by the release of gas bubbles, typically nitrogen, from its dissolved state in the body. This occurs due to a rapid decrease in barometric pressure, such as during a diver's ascent from a deep dive or a pilot's ascent to high altitudes in an unpressurized aircraft.
Symptoms range from joint pain, fatigue, and skin irritation in mild cases, to shortness of breath, chest pain, paralysis, and confusion in more severe instances. Relief is usually achieved through recompression in a hyperbaric chamber, followed by gradual decompression, though this may not always reverse tissue damage. It can be prevented by allowing sufficient decompression time for the excess nitrogen gas to be expelled naturally.
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When and why can decompression sickness happen?
Decompression sickness, also known as "the bends," occurs when dissolved gases, typically nitrogen, form bubbles in the body's tissues due to a rapid decrease in pressure. This can happen to divers ascending too quickly from deep dives, aviators in unpressurized aircraft ascending to high altitudes rapidly, or individuals working in environments with increased atmospheric pressure. Insufficient decompression time causes nitrogen to be released as gas bubbles in the body, leading to decompression sickness. Symptoms range from joint pain, fatigue, and skin irritation to shortness of breath, chest pain, paralysis, and confusion. Recompression in a hyperbaric chamber, followed by gradual decompression, is a typical treatment.
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What are common symptoms of decompression sickness?
Decompression sickness, also known as the bends or caisson disease, occurs due to rapid reduction in barometric pressure, causing nitrogen bubbles to form in tissues and fluids.
Common symptoms include joint pain, which can be severe and restrict movement, leading to the term "bends" because affected individuals may be unable to straighten their joints. Other symptoms include fatigue, itching, and skin burning.
In severe cases, decompression sickness can manifest as shortness of breath, chest pain, paralysis, and confusion. The formation of bubbles in the nervous system can result in difficulties with muscle coordination, sensory abnormalities (diversā staggers), numbness, speech defects, and personality changes. Respiratory symptoms such as excessive coughing and breathing difficulties (the chokes), along with chest pain and shock, may also occur, signaling a critical emergency.
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How does decompression sickness affect the body?
Decompression sickness, also known as "the bends," arises from a rapid reduction in pressure, causing dissolved gases, typically nitrogen, to form bubbles in tissues and blood vessels. These bubbles can have various mechanical and surface effects on the body.
The impact of decompression sickness varies based on where the bubbles form. In the nervous system, which is composed of about 60 percent lipids, bubbles can cause paralysis, convulsions, difficulties with muscle coordination, sensory abnormalities, numbness, speech defects, and personality changes. When bubbles accumulate in the joints, pain is usually severe and mobility is restricted. In the respiratory system, nitrogen bubbles can lead to excessive coughing and difficulty in breathing.
Treatment typically involves recompression in a hyperbaric chamber followed by gradual decompression.
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Who is most at risk for decompression sickness?
Individuals at high risk for decompression sickness include underwater divers and pilots in unpressurized aircraft, as well as caisson workers. These individuals are susceptible because their activities expose them to pressure changes different from normal atmospheric pressure. Decompression sickness occurs when gas bubbles form in the body due to a rapid transition from a high-pressure environment to one of lower pressure. The condition can be prevented by allowing sufficient decompression time for the excess nitrogen gas to be expelled naturally.
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How can decompression sickness be treated and prevented?
Decompression sickness is treated through recompression in a hyperbaric chamber followed by gradual decompression, though this may not always reverse tissue damage. Emergency treatment involves rapid recompression in a compression chamber, with gradual decompression afterward.
Prevention involves allowing sufficient decompression time for excess nitrogen gas to be expelled naturally. Sufficient decompression time is needed so that gases can leave the tissues, which can prevent bubble formation.
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decompression sickness, physiological effects of the formation of gas bubbles in the body because of rapid transition from a high-pressure environment to one of lower pressure. Pilots of unpressurized aircraft, underwater divers, and caisson workers are highly susceptible to the sickness because their activities subject them to pressures different from the normal atmospheric pressure experienced on land.
Physiological basis
At atmospheric pressure the body tissues contain, in solution, small amounts of the gases that are present in the air. When a pilot ascends to a higher altitude, the external pressures upon his body decrease, and these dissolved gases come out of solution. If the ascent is slow enough, the gases have time to diffuse from the tissues into the bloodstream; the gases then pass to the respiratory tract and are exhaled from the body.
Underwater divers breathing compressed air are also faced with the possibility of a form of decompression sickness known as the bends. As they descend into the water, the external pressure increases proportionally to the depth. The compressed air that is breathed is equal in pressure to that of the surrounding water. The longer a diver stays down and the deeper the dive, the more compressed gas that is absorbed by the body. When the diver ascends, time must be allowed for the additional gases to be expelled slowly or they will form bubbles in the tissues.
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The major component of air that causes decompression maladies is nitrogen. The oxygen breathed is used up by the cells of the body and the waste product carbon dioxide is continuously exhaled. Nitrogen, on the other hand, merely accumulates in the body until the tissue becomes saturated at the ambient pressure. When the pressure decreases, the excess nitrogen is released.
Physiological effects and symptoms
Nitrogen is much more soluble in fatty tissue than in other types; therefore, tissues with a high fat content (lipids) tend to absorb more nitrogen than do other tissues. The nervous system is composed of about 60 percent lipids. Bubbles forming in the brain, spinal cord, or peripheral nerves can cause paralysis and convulsions (diversā palsy), difficulties with muscle coordination and sensory abnormalities (diversā staggers), numbness, nausea, speech defects, and personality changes. When bubbles accumulate in the joints, pain is usually severe and mobility is restricted. The term bends is derived from this affliction, as the affected person commonly is unable to straighten joints.
Small nitrogen bubbles trapped under the skin may cause a red rash and an itching sensation known as diversā itches. Usually these symptoms pass in 10 to 20 minutes. Excessive coughing and difficulty in breathing, known as the chokes, indicate nitrogen bubbles in the respiratory system. Other symptoms include chest pain, a burning sensation while breathing, and severe shock.
Treatment
Relief from decompression sickness usually can be achieved only by recompression in a hyperbaric chamber followed by gradual decompression, but this process is not always able to reverse damage to tissues.
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