Decompression Sickness

A condition resulting from the formation of gas bubbles in the blood and tissues following a rapid decrease in pressure

  • Deep-sea diving is a risk factor
  • Age, gender, and genetics are not significant factors

Decompression sickness, also known as “the bends”, usually occurs when a person surfaces too quickly after a deep dive underwater. The condition may also result from working in pressurized tunnels, being exposed to sudden aircraft decompression at high altitude, or flying too soon after scuba diving.

At normal atmospheric pressure, a certain amount of gas is dissolved in the blood and other tissues. More gas accumulates in the tissues of divers due to the high-pressure gas mixture they breathe while underwater. If, during a slow ascent to the water’s surface, the surrounding pressure is lowered gradually, excess gas is carried to the lungs by the blood and is exhaled. If the reduction in pressure during ascent is too rapid, gas cannot be carried away gradually and bubbles form in the blood and tissues, causing decompression sickness. Decompression sickness in people other than divers is also due to the formation of gas bubbles in blood and tissues.

What are the symptoms?

Symptoms usually occur within a few hours of the pressure being reduced but may take up to 24 hours to develop. They often include:

  • Itching.

  • Mottling of the skin.

  • Severe pains in the larger joints, particularly the shoulders and knees.

  • Headache.

Gas bubbles may lodge in the blood vessels that supply the heart or lungs, causing a tight pain across the chest. If bubbles lodge in the brain or spinal cord, weakness in the legs or problems with vision and balance may occur.

What might be done?

If you have symptoms of decompression sickness, you should be taken to a recompression chamber immediately. Once you are in the sealed chamber, air is pumped in to increase the pressure (recompression). The increased pressure forces the gas bubbles to redissolve into the tissues, thereby relieving the symptoms. Decompression can then be carried out slowly over several hours to prevent bubbles from forming again.

Prompt treatment usually leads to a full recovery. Serious, untreated cases may cause long-term paralysis. People who have repeated episodes of decompression sickness and recompressions may develop progressive degeneration of their bones and joints.

From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.

The subjects, conditions and treatments covered in this encyclopaedia are for information only and may not be covered by your insurance product should you make a claim.

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