Decompression Illness (DCI) is a term generally used to describe illness after a decrease in the ambient pressure that a body is exposed to. Decompression Illness is usually experienced by divers, but it is not limited to in water diving. Any person exposed to great pressure changes (such as scuba divers, aviators, astronauts and compressed-air workers) may be at risk of Decompression Illness.

DCI consists of the composition of Decompression sickness (DCS) and Arterial Gas Embolism (AGE). DCS usually results from bubbles causing damage to tissues, while AGE results from bubbles entering the blood vessels and causing tissue damage by blocking blood flow.

Decompression sickness

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Decompression sickness is usually the result of inadequate decompression following exposure to increased pressure. The disease is usually mild and not an immediate threat. However, it must be noted that serious injury can occur. As a general rule, the sooner treatment is initiated, the better the chance for a full recovery.

Decompression sickness is also known as "the bends" or Caisson Disease.

Mechanism of injury

During a dive, the body tissues absorb nitrogen in proportion to the surrounding pressure. As long as the diver remains at pressure the excess nitrogen is exhaled by the lungs. However, if the body is subjected to a rapid loss of pressue (such as rapid ascent) the nitrogen will expand into bubbles and diffuse into the tissue and bloodstream before it has a chance to be exhaled by the lungs.

Once there is an accumulation of sufficient nitrogen, bubbles will form as the pressure upon the nitrogen is decreased. If the bubbles form in or near joints, this will cause joint pains which contributed to the nickname of the "bends" .

Bubbles may form in any part of the body, but form in different types of tissue at different concentrations. For example, fatty tissue absorbs nitrogen at a much faster rate than muscle or bone tissue, but that fatty tissue also off-gasses the nitrogen at a much faster rate. The different concentrations of nitrogen in the different tissues explain why symptoms may not occur until the diver has been on the surface for quite awhile.

Numbness, paralysis and disorders of higher cerebral function may also occur as the bubble from the various tissues increase in size.

Symptoms

• Fatigue
• Skin itch
• Pain in joints or muscles
• Dizziness, vertigo, ringing in the ears
• Numbness, tingling and paralysis
• Shortness of breath

Signs

• Skin rash
• Paralysis, muscle weakness
• Difficulty in urinating
• Confusion, personality changes, bizarre behavior
• Loss of memory, tremors
• Staggering
• Bloody, frothy sputum
• Collapse or unconsciousness

Signs and symptoms can appear immediately after surfacing, but may take up to a day or two to appear. Delayed onset is rare, but does happen.

Arterial Gas Embolism

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Arterial Gas Embolism is usually the result of some injury to the lungs causing air bubbles to "leak" into the bloodstream.

Mechanism of injury

If a diver ascends without exhaling, the gas in the lungs will expand due to the reduced pressure surrounding the lungs and may rupture lung tissue. This is pulmonary barotrauma which releases gas bubbles into the arterial circulation. This will cause the bubbles to be circulated through the body via the bloodstream. If the bubbles reach the brain and damage it, this is termed as CAGE (Cerebral Arterial Gas Embolism).

A person suffering from AGE may surface unconscious. This does not mean that any person who is conscious on surfacing is excluded from the possibility of AGE.

Symptoms

• Dizziness
• Blurring of Vision
• Areas of decreased sensation
• Chest pain
• Disorientation

Signs

• Bloody froth from mouth or nose
• Paralysis or weakness
• Convulsions
• Unconsciousness
• No breathing
• Death

First aid

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First aid for DCI is administered by:

• Monitoring the victim for responsiveness, airway, breathing and circulation, to resucitate if necessary. The victim should be laid on his or her back or (for drowsy, unconscious, or nauseated victims) on their side.
• Administration of 100% oxygen a soon as possible.
• Seeking of immediate medical aid and consultation with a diving medical specialist.

Details of recent dives and responses to first aid treatment should be recorded and provided to the treating medical specialist. The diving details should include depth and time profiles, breathing gases used and surface intervals.

The victim may be allowed to drink water or isotonic fluids only if they are responsive, stable, and not suffering from nausea or stomach pain. Administration of saline via intravenous drip is preferable.

Entonox should not be given.

Treatment

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Very often hyperbaric oxygen therapy in a recompression chamber in needed. With some types of lung barotrauma, surgery is required.

References

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• Diving First Aid Manual, John Lippmann and Stan Bugg, DAN SEAP Membership Edition
• The Diving Emergency Handbook, John Lippmann and Stan Bugg, ISBN 0946020183

Diving medicine