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Causes of Air embolism
Air embolism is very rare. It usually occurs in divers who have breathed high-pressure air at depth and who then surface without allowing the expanding air to escape freely. It is commonly known as 'the bends'.
This can happen if divers run out of air and hold their breath while coming to the surface, or if they surface too quickly. The air in the lungs expands and a bubble of nitrogen can enter the veins that carry blood back to the heart. From there it is pumped to the brain and elsewhere.
Air embolism can sometimes be a result of an injury in which the chest is crushed, such as in a car crash. It is also, rarely, caused by medical procedures. Procedures with a risk of air embolism include surgery to the arteries or veins, injections during surgery, large blood transfusions, and open-heart surgery. In these cases, it is possible for air to be introduced directly to a blood vessel from outside the body. However, precautions are always taken to prevent this; for example, a syringe is pressed until there is no air in it, before the injection is given.
