Decompression Illness (DCI) is a blanket term which encompasses decompression sickness (DCS) and Arterial Gas Embolism (AGE). This general term is used because of the manifestations and management of the two disorders are often identical due to the difficulty in distinguishing between them.

Decompression Illness is caused by the presence of gas bubbles in our bodies. Bubbles can enter the bloodstream if a pressure build-up in the lungs forces air from the lungs into the blood. This is known as arterial gas embolism and can result from breath-holding or inadequate exhalation on ascent; or trapping of air in the lungs due to asthma, mucus, water inhalation, laryngospasm, cough or cold.

On the other hand, the bubbles in the blood and body tissues can result from excess nitrogen (or another inert gas) from inadequate decompression after a dive. This is known as decompression sickness.

DCI can and does occur on dives that are well within the no stop limits of dive tables and dive computers because they cannot accurately predict the formation and distribution of bubbles in our bodies.

Bubbles in the blood and body tissues can block or damage blood vessels, reducing the blood supply to various parts of the body. They can also interfere with nerve function and cause undesirable chemical changes in the blood which further reduces effective circulation. The following predisposing factors may increase a diver's likelihood of getting decompression illness:
• Repetitive diving (especially multiday repetitive diving)
• Deeper diving
• Rapid or multiple ascents
• Exercise during or after the dive
• Flying after diving
• Presence of a patent foramen ovale (PFO)
• Dehydration (e.g. seasickness, alcohol, diving in hot weather)
• Obesity
• Fatiggue, lack of fitness, illness, previous injury
• Being cold
• Age - risk may increase with age
• Carbon dioxide excess
• Decompression stop diving
• Breath-holding during ascent
• Lung disease (due to increased risk of pulmonary barotrauma and consequent AGE)

Note:
If symptoms to those of decompression illness are present after diving, never exclude decompression illness because of what may appear to be a safe dive according to the dive computer or tables.

Common Signs & Symptoms of Decompression Illness
Although these usually occur within six hours of diving, they may also develop 24 to 48 hours after the dive, or even later if there is altitude exposure. Even though the symptoms of DCI sometimes disappear spontaneously, particularly if oxygen is breathed, medical consultation, evaluation and usually recompression are required to minimise tissue damage and later recurrence of symptoms.
• Chest torso or back pain; discomfort in the joints
• Dizziness
• Extreme fatigue & weakness
• Headaches
• Malaise
• Nausea
• Numbness/tingling
• Rash (often mottled)

Other Signs and Symptoms of Decompression Illness
• Blotchy skin
• Confusion
• Convulsions
• Coughing
• Death
• Difficulty breathing
• Difficulty passing urine
• Hearing loss
• Itch
• Lack of coordination
• Loss of balance/bladder control
• Paralysis
• Personality change
• Ringing in ears
• Speech disturbances
• Visual disturbances

First Aid Treatment for Decompression Illness
• Monitor consciousness, airway and breathing and begin CPR if necessary
• Lay the diver down flat and maintain the airway
• A diver who is nauseated, vomiting or not fully conscious should be placed on the side
• Administer 100% oxygen as soon as possible
• Seek medical aid immediately. Arrange for consultation between the attending medical personnel and a diving medical specialist
• Transfer to a recompression chamber may be required
• A conscious and stable diver may drink non-alcoholic fluid such as water, isotonic/electrolytes
• Record the details of dive profile(s), first aid given and the diver's response to first aid

Special Considerations for Decompression Illness
Intravenous (IV) fluids are preferable. Oral fluids are given only if the diver is conscious, stable and is not suffering from stomach pain, nausea or vomiting and is able to urinate. record the amount and type of fluid given. Record urinary output and check for bladder distension.