Find information on medical topics, symptoms, drugs, procedures, news and more, written in everyday language.

* This is the Consumer Version. *

Air Embolism

by Alfred A. Bove, MD, PhD

Air embolism is blockage of blood supply to organs caused by bubbles in an artery.

  • Within a few minutes of reaching the surface, divers can lose consciousness or develop symptoms similar to those of a stroke.

  • People are given oxygen, made to lie down, and sent as soon as possible to a recompression chamber.

Air bubbles can enter the blood after pulmonary barotrauma (see Pulmonary barotrauma) or decompression sickness (see Decompression Sickness) and travel to any organ in the body and block small blood vessels, most commonly those of the brain, but also of the heart, skin, and kidneys. A very large air embolism can block flow through the heart chambers or the large arteries.


Air embolism is a leading cause of death among divers. Symptoms of air embolism usually appear within a few minutes of reaching the surface. Air embolism to the brain often resembles a stroke, resulting in confusion and partial paralysis or loss of sensation. Some people have sudden loss of consciousness or seizures. Severe air embolism can lead to shock (see Shock) and death.


Divers who lose consciousness during ascent or very shortly afterward are assumed to have air embolism. They must be treated promptly. Imaging tests are sometimes done but are not always reliable.


People are immediately made to lie down and given oxygen. They must be returned as soon as possible to a high-pressure environment, so that the air bubbles are compressed and forced to dissolve in the blood. Many medical centers have high-pressure (recompression or hyperbaric) chambers for this purpose.

Flying, even at a low altitude, reduces atmospheric pressure and allows bubbles to expand further, but it can be justified if it saves substantial time in getting people to a suitable chamber. If possible, people should fly in a plane pressurized to sea level, or the plane should not fly above 2,000 feet (610 meters).