| WHAT IS ARTERIAL GAS EMBOLISM? Arterial Gas Embolism (AGE) is the most serious medical problem related to pulmonary expansion barotrauma. It is a major cause of sport diving deaths (Arthur 1987; Kizer 1987). AGE accounts for about 40% of the case load at active dive accident treatment centers in the U.S. (Kizer 1987). AGE is thought to occur when alveoli rupture and air enters the pulmonary veins, from where it travels through the left heart chambers and into the arterial circulation. Despite this presumed mechanism AGE victims do not usually show obvious evidence of lung rupture when their chest x-rays are examined (Kizer 1987; Gorman 1989; Williams 1990). AGE characteristically manifests within minutes of surfacing. In cases of AGE reported to the national Divers Alert Network in 1988, 78% had their first symptoms within five minutes and 88% within 10 minutes (DAN 1988). The early onset of symptoms is in contrast to decompression sickness (discussed in Section G). Decompression sickness is caused by a different type of bubbles (pure nitrogen) and causes symptoms that come on more gradually than AGE. The brain is the most commonly affected major organ in AGE, although air emboli can also block coronary arteries and lead to heart attack (Kizer 1987). Cerebral air embolism can present with sudden unconsciousness or acute neurological deficit (stroke). Other neurological symptoms include severe headache, difficulty speaking, and visual loss (Dick 1985). The major alternative diagnosis to AGE is decompression sickness but treatment is the same for both conditions: recompression in a hyperbaric chamber. WHAT IS TREATMENT OF AGE? First aid treatment of suspected AGE requires putting the patient in comfortable position; usually this will be supine and flat. The head-lower-than-the-body position (so-called Trendelenburg position) was once thought to prevent embolism to the brain, but this has not been substantiated and is no longer recommended (Butler 1988). Other first aid includes administering a high concentration of oxygen (see Section H) and plenty of fluids. Arrangements should be made to transport the victim to the appropriate medical facility (See Appendix A). Although symptoms of AGE may improve after first aid, recompression in a chamber is still considered mandatory (Kindwall 1983; Kizer 1987; Green 1987), for two reasons. First, patients with AGE can relapse after initial improvement. Second, AGE may be accompanied by decompression sickness, a condition more insidious in onset and which also responds to recompression therapy. One review found a 12% prevalence of both conditions in seriously ill patients referred for recompression therapy (Green 1987). Once AGE is suspected, the patient should be referred to a hyperbaric chamber. |
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