Air Embolism - in Humans and Animals

In Humans and Animals

Small amounts of air often get into the blood circulation accidentally during surgery and other medical procedures (for example a bubble entering an intravenous fluid line), but most of these air emboli enter the veins and are stopped at the lungs, and thus a venous air embolism that shows any symptoms is very rare.

For venous air embolisms, death may occur if a large bubble of gas becomes lodged in the heart, stopping blood from flowing from the right ventricle to the lungs (this is similar to vapor lock in engine fuel systems). However, experiments in animals show that the amount of gas necessary for this to happen is quite variable, and also depends on several other factors, such as body position. Very large and symptomatic amounts of venous air emboli may also occur in rapid decompression in severe diving or decompression accidents, where they may interfere with circulation in the lungs and result in respiratory distress and hypoxia.

Gas embolism into an artery, termed arterial gas embolism (AGE), is a more serious matter than in a vein, because a gas bubble in an artery may directly stop blood flow to an area fed by the artery. The symptoms of 'AGE' depend on the area of blood flow, and may be those of stroke or heart attack if the brain or heart, respectively, is affected. The amount of arterial gas embolism that causes symptoms depends on location, but in the brain may be a bubble with a volume only a fraction of a milliliter.