Decompression Illness (DCI) describes a collection of symptoms arising from decompression of the body.
DCI is caused by two different mechanisms, which result in overlapping sets of symptoms. The two mechanisms are:
- Decompression sickness (DCS), which results from gas dissolved in body tissue under pressure precipitating out of solution and forming bubbles on decompression. It typically afflicts scuba divers on poorly managed ascent from depth or aviators flying in inadequately pressurised aircraft.
- Arterial gas embolism (AGE), which is gas bubbles in the bloodstream. In the context of DCI these may form either as a result of precipitation of dissolved gas into the blood on depressurisation, as for DCS above, or by gas entering the blood mechanically as a result of pulmonary barotrauma. Pulmonary barotrauma is a rupturing of the lungs by internal over-pressurisation caused by the expansion of air held in the lungs on depressurisation such as: a scuba diver ascending while holding the breath or; the explosive decompression of an aircraft cabin or other working environment.
Mechanisms of injury 
- Refer to the main article decompression sickness for the mechanism of injury behind DCS.
- Refer to the main article arterial gas embolism for the mechanism of injury behind AGE.
Signs and symptoms 
Below is a summary comparison of the signs and symptoms of DCI arising from its two components: Decompression Sickness and Arterial Gas Embolism. A more detailed account of the signs and symptoms of Decompression Sickness can be found here.
|Decompression sickness||Arterial Gas Embolism|
|Skin rash||Bloody froth from mouth or nose|
|Paralysis, muscle weakness||Paralysis or weakness|
|Difficulty in urinating||Convulsions|
|Confusion, personality changes, bizarre behaviour||Unconsciousness|
|Loss of memory, tremors||No breathing|
|Collapse or unconsciousness|
|Skin itch||Blurring of Vision|
|Pain in joints or muscles||Areas of decreased sensation|
|Dizziness, vertigo, ringing in the ears||Chest pain|
|Numbness, tingling and paralysis||Disorientation|
|Shortness of breath|
First aid 
First aid is common for both DCS and AGS:
- Monitor the patient for responsiveness, airway, breathing and circulation, resuscitate if necessary.
- Treat for shock.
- Lay the patient on their back, or for drowsy, unconscious, or nauseated victims, on their side.
- Administer 100% oxygen as soon as possible.
- Seek immediate medical assistance, locate a hospital with hyperbaric facilities and plan for possible transport.
- Allow the patient to drink water or isotonic fluids only if responsive, stable, and not suffering from nausea or stomach pain. Administration of intravenous saline solution is preferable.
- Record details of recent dives and responses to first aid treatment and provide to the treating medical specialist. The diving details should include depth and time profiles, breathing gases used and surface intervals.
Treatment for the Decompression Sickness and the Arterial Gas Embolism components of DCI may differ significantly. Refer to the separate treatments under those articles.
See also 
- Diving First Aid Manual, John Lippmann and Stan Bugg, DAN SEAP Membership Edition
- The Diving Emergency Handbook, John Lippmann and Stan Bugg, ISBN 0-946020-18-3