A syndrome occurring in people working under high pressure in diving bells or at great depths or altitudes with breathing apparatus. On return to normal atmospheric pressure nitrogen dissolved in the bloodstream expands to form bubbles, causing pain (the bends) and blocking the circulation in small blood vessels in the brain and elsewhere (decompression sickness). Pain, paralysis, and other features may be eliminated by returning the victim to a higher atmospheric pressure and reducing this gradually, so causing the bubbles to redissolve. Chronic compressed air illness may cause damage to the bones (avascular necrosis), heart, and Kings.
Also known as caisson disease, this affects workers operating in compressed-air environments, such as underwater divers and workers in caissons (such as an ammunition wagon, a chest of explosive materials, or a strong case for keeping out the water while the foundations of a bridge are being built; derived from the French caisse, meaning case or chest). Its chief symptoms are pains in the joints and limbs (bends); pain in the stomach; headache and dizziness; and paralysis. Sudden death may occur. The condition is caused by the accumulation of bubbles of nitrogen in different parts of the body, usually because of too-rapid decompression when the worker returns to normal atmospheric pressure — a change that must be made gradually.