Underwater diving accidents

Air embolism

An air embolism occurs when there is a rupture in the barrier between the microscopic air space of a lung and its corresponding blood vessel, which carries oxygenated blood back to the heart (where it can be distributed to the body). With air embolism, bubbles of air are released into the arterial bloodstream, where they act as physical barriers to circulation, and can cause a stroke (see page 165), heart attack (see page 57), headache, spinal cord injury, and/or confusion. Typically, the victim is a scuba (self-contained underwater breathing apparatus) diver who ascends too rapidly without exhaling, thus allowing overexpansion of the lungs—and rupture of the tissue—as the external water pressure decreases with ascent. In other words, as a diver ascends from the depths, the air in their lungs (which was delivered from the scuba tank through a regulator at a pressure equal to the surrounding water pressure on the lungs, thereby allowing lung expansion) expands. If the rate of exhalation does not keep pace with this lung expansion, the increased pressure within the lungs causes air to be forced through the lung tissue, where it appears in the bloodstream in bubble form and travels directly to the heart. From the heart, the air circulates to and might occlude critical small blood vessels that supply the heart, brain, and spinal cord.

The most common symptoms are unconsciousness, confusion or disorientation, seizures, and/or chest pain immediately on surfacing. Others include dizziness, visual blurring, loss of vision, headache, abnormal personality, confusion, total or partial paralysis, and weakness. Any disorder that appears in a previously normal diver more than 10 minutes after surfacing is probably not due to air embolism.

Anyone suspected of having suffered an air embolism should be placed in a head-down position (with the body at a 15- to 30-degree tilt), turned onto their left side, assisted with breathing, if necessary (see page 25), and immediately transported to an emergency facility. If oxygen (see page 431) is available, it should be administered by face mask at a flow rate of 10 liters per minute. The treatment for arterial gas embolism is recompression in a hyperbaric oxygen chamber, which pressurizes the victim’s environment and shrinks the bubbles. This must be accomplished as rapidly as possible to save the victim’s life and to minimize disability. A portable recompression chamber manned by trained personnel might be used to initiate field treatment. If the victim is capable of purposeful swallowing, administer one adult aspirin by mouth.

If the air that expands on ascent does not rupture into a blood vessel and become an air embolism, it can rupture into the actual lung tissues or into the pleural space between the lung and the inside of the chest wall and cause a collapsed lung (pneumothorax) (see page 47). Other symptoms include air that escapes into the soft tissues, so that there is swelling of the chest and neck, and sometimes a “Rice Krispies” feel to the skin. If the air dissects into the neck, it can cause hoarseness, difficulty swallowing, and sore throat. In this case, oxygen administration is advised. Recompression in a hyperbaric chamber is not advised for a pneumothorax unless there are also severe symptoms associated with an air embolism.

When transporting a victim of air embolism, it’s recommended that you use an aircraft that can be pressurized to 1 atmosphere or keep the flight altitude (in an unpressurized aircraft) below 1000 ft (305 m).