Decompression Illness


DCS, as it is commonly know, is caused by a build up of nitrogen bubbles in the body. When we breathe, approximately 79 of the air we’re breathing is nitrogen. As we descend in water, the pressure around our bodies increases, causing nitrogen to be absorbed into our body tissues. If a diver ascends too fast and the nitrogen escapes the body tissue too quickly it becomes bubbles in the body and this leads to Decompression Sickness. The bubbles must normally be on the arterial side of the circulatory system to be harmful – they are usually harmless on the venous side. There are several types of Decompression Sickness:  


If a diver surfaces without exhaling, air trapped in the lungs expands with ascent and may rupture lung tissue – called pulmonary barotrauma – which releases gas bubbles into the arterial circulation. This distributes them to body tissues in proportion to the blood flow. Since the brain receives the highest proportion of blood flow, it is the main target organ where bubbles may interrupt circulation if they become lodged in small arteries.

Decompression Sickness

A disorder caused by the formation of nitrogen bubbles in the blood and tissues following a sudden drop in the surrounding pressure and characterized by joint pain, skin irritation, cramps, numbness, and, in severe cases, paralysis. It occurs especially in deep-sea divers when ascending rapidly from a dive. Decompression sickness is often called “the bends.” When scuba diving, additional oxygen and nitrogen dissolve in body tissues.  The additional oxygen is consumed by the tissues,

but the excess nitrogen must be washed out by the blood during decompression.  During or after ascent this excess nitrogen gas can form bubbles in the tissues, analogous to the carbon dioxide bubbles that form when a carbonated beverage container is opened.  These bubbles may then cause symptoms that are referred to as decompression sickness (“DCS” or “the bends”).

  • Trapping of gas within the lungs during ascent, either because the lung is diseased or because of breath-holding, can cause bubbles to be forced into the bloodstream (“arterial gas embolism” or “AGE”), where they can block the flow of blood or damage the lining of blood vessels supplying critical organs such as the brain.
  • AGE can also occur in non-divers, due to entry of air into the body, such as during medical diagnostic or therapeutic procedures.
  • Symptoms of DCS or AGE can include joint pain, numbness, tingling, skin rash, extreme fatigue, weakness of arms or legs, dizziness, loss of hearing, and in serious cases, complete paralysis or unconsciousness.

Arterial Gas Embolism

This is arterial gas embolism, or AGE, considered the more serious form of DCI. In some cases the diver may have made a panicked ascent, or he may have held his breath during ascent. However, AGE can occur even if ascent appeared completely normal, and pulmonary disease such as obstructive lung disease may increase the risk of AGE.

The most dramatic presentation of air embolism is the diver who surfaces unconscious and remains so, or the diver who loses consciousness within 10 minutes of surfacing. In these cases, a true medical emergency exists, and rapid evacuation to a treatment facility is paramount.

On the other hand, air embolism may cause less spectacular symptoms of neurological dysfunction, such as sensations of tingling or numbness, a sensation of weakness without obvious paralysis, or complaints of difficulty in thinking without obvious confusion in individuals who are awake and easily aroused. In these cases, there is time for a more thorough evaluation by a diving medical specialist to rule out other causes of symptoms. Like DCS, mild symptoms may be ascribed to causes other than the dive, which only delays treatment. Sometimes symptoms may resolve spontaneously and the diver will not seek treatment. The consequences of this are similar to untreated DCS: residual damage to the brain may occur, making it more likely there will be residual symptoms after a future bout of AGE, even if the later bout is treated.

Learn the Signs and Symptoms