Air or Gas Embolism

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Air or gas embolism is the presence of gas bubbles in the bloodstream that obstruct circulation. It may occur with decompression from increased pressure — typically occurring in ascending divers who have been breathing compressed air. If a diver does not fully exhale upon ascent, the air in the lungs expands as the pressure decreases, over-inflating the lungs and forcing bubbles of gas (emboli) into the bloodstream. When the moving bubbles reach the arteries to the brain, the blood blockage causes unconsciousness. Gas embolism is second only to drowning as a cause of death among divers.

Gas embolism may also result from trauma or medical procedures such as catheterization and open-heart surgery that allows air into the circulatory system.

The primary symptom of gas embolism is immediate loss of consciousness; it may or may not be accompanied by convulsions. Any unconscious diver should be assumed to be the victim of gas embolism, regardless of whether consciousness was lost during or promptly after ascent. A doctor may also find pockets of air in the chest around the lungs and sometimes a collapsed lung from over-inflation and rupture. Coughing up blood or a bloody froth around the mouth are visible signs of lung injury.

Hyperbaric oxygen therapy works to deflate the gas bubbles in the bloodstream so blood flow is restored to the brain and other organs. It also helps to force out other gases so bubbles don’t reform and decreases swelling in the injured area.

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