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Decompression Sickness


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Decompression Sickness

By William G. Cowley

While there’s always some minimal possibility that decompression sickness (DCS) will occur, even when you do everything right, you should be aware that the primary reason divers suffer DCS is from diver error. These errors cause the diver to absorb more nitrogen than he should, of fail to release nitrogen safely before surfacing. These include misuse of, of failure to use dive tables or dive computer, exceeding proper ascent rates, omitting emergency decompression stops, running out of air (which can lead to exceeding proper ascent rates and omitting emergency decompression/safety stops), ignoring factors that predispose divers to DCS, and failure to follow conservative diving practices.

A diver suffering from DCS may show various signs and experience various symptoms, depending upon where bubbles form in his body.

Signs and Systems

Signs include:

  • Favoring an arm or leg, or rubbing a joint.
  • Paralysis
  • Unconsciousness
  • Staggering
  • Collapse
  • Coughing spasms
  • Blotchy skin Rash

Symptoms include:

  • Pain, often in the limbs, and also often, but not necessarily in the joints. The pain can move over time.
  • Numbness, tingling or paralysis.
  • Unusual fatigue or weakness
  • Skin itch
  • Shortness of breath


In the majority of instances, DCS occurs at the surface within one to two hours of the dive. However, it can occur underwater at a shallow depth, and symptoms can be delayed as long as 48 hours. Furthermore, DCS may become more likely based on these factors:

    • Excess fat tissue. Fat tissue holds more dissolved nitrogen.
    • Age. As a person ages, the circulatory system becomes less efficient, therefore slowing nitrogen elimination. People also tend to have more fat tissue as they get older.
    • Heavy exertion before, during or after a deep dive. Exertion before or after the dive can promote micro-bubbles that grow as excess nitrogen dissolves into them. Exertion during the dive speeds up the circulation, accumulating more nitrogen than normal.
    • Injuries and illness. These can effect circulation and the ability to eliminated nitrogen.
    • Dehydration. This reduces the quantity of blood circulating to eliminate nitrogen.
    • Use of Alcohol. Before the dive this can cause dehydration and immediately after the dive it alters circulation, possibly promoting bubble growth.
    • Cold water. To save heat, the body restricts circulation to parts of the body, thereby eliminating nitrogen less effectively.
    • Hot showers or baths immediately after a dive. These cause skin capillaries to dilate, altering circulation.
    • Carbon dioxide increase. This is usually caused by exertion or skip-breathing (breath holding) and interferes with the blood’s ability to carry nitrogen.
    • Exposure to altitude. Flying or diving to altitude after diving, or diving at altitude requires special guidelines because dive tables and computers base their calculations on surfacing at sea level. Follow current recommendations when flying or driving to altitude, get the proper training in the PADI Altitude diver Specialty course.

To prevent DCS, adhere to safe, conservative diving practices, Stay well within the limits of your dive table or computer, and make safety stops at the end of every dive.


Emergency Care for Decompression Sickness

If a diver is suspected of decompression sickness, and you are not diving with professional supervision, such as on a charter boat, you should know the steps to take.

Have the diver lie down and administer 100 percent oxygen, if available. Oxygen helps eliminate nitrogen and it raises the blood oxygen level to assist tissues receiving less than normal due to bubble blockage. For most cases, have the diver lie on his back or left side, whichever is more comfortable, but don’t let him sit up.

In severe cases, the diver may need CPR, which requires laying him on his back. An unconscious breathing diver should be laid on his left side.

After beginning first aid – or before if the diver is unresponsive and you are alone – immediately contact the local emergency medical system. In many areas, specialized diver emergency networks can assist you and local medical personnel in locating the chamber and consult in treating the diver, The Divers Alert Network (DAN) provided this service in the United States and Caribbean. In the South Pacific, the Divers Emergency Service (DES) fills this important role.