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.
(See also Overview of Diving Injuries.)
Air bubbles can enter arterial or venous blood (air embolism—see Unusual Types of Emboli) after pulmonary (lung) barotrauma or decompression sickness. When bubbles occur in arteries, they may 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 in the heart chambers or the large arteries. When bubbles occur in veins, they may pass into the arteries through heart defects such as a patent foramen ovale or atrial septal defect.
Arterial gas embolism (sometimes referred to as AGE in the diving literature) is a leading cause of death among divers.
Symptoms of arterial gas embolism usually appear within a few minutes of reaching the surface. Arterial gas 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 arterial gas embolism can lead to shock and death.
Other symptoms may result from an underlying pulmonary barotrauma or decompression sickness, or from arterial gas embolism in any of the following:
Divers who lose consciousness during ascent or very shortly afterward are assumed to have arterial gas 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 fly at as low an altitude as is consistent with safety. Breathing oxygen is also recommended.