Air or Gas Embolism
Richard E. Moon, M.D.
Gas embolism occurs when gas bubbles enter arteries or veins. Arterial gas embolism (AGE) was classically described during submarine escape training, in which pulmonary barotraumas occurred during free ascent after breathing compressed gas at depth. Pulmonary barotrauma and gas embolism due to breath holding can occur after an ascent of as little as one meter. AGE has been attributed to normal ascent in divers with lung pathology such as bullous disease and asthma. Pulmonary barotrauma can also occur as a result of blast injury in or out of water, mechanical ventilation, penetrating chest trauma, chest tube placement, and bronchoscopy.
HBOT to treat gas embolism remains the definitive treatment for gas embolism. Indications for treatment include neurological manifestations or cardiovascular instability. A review of 597 published cases of arterial gas embolism reveals superior outcomes with the use of HBOT compared to non-recompression treatment. HBOT treatment is not required for asymptomatic VGE, however it can effect clinical improvement in patients with secondary pulmonary edema. Gas bubbles have been known to persist for several days and there are many reports noting success when HBO2 treatments were begun after delays of hours to days. A trial of HBOT therapy may be indicated even for those patients coming to a hyperbaric unit after a significant delay following the inciting event. Because of the tendency for patients with AGE to deteriorate after apparent recovery, early HBOT is recommended even for patients who appear to have spontaneously recovered. One author has suggested that the presence or absence of air detectable by brain computed tomography should be used as a criterion for HBOT therapy. However, timely administration of HBOT usually causes some clinical improvement, even in the absence of demonstrable air. Performing brain imaging usually delays the initiation of appropriate HBOT treatment and rarely serves a useful clinical purpose.
In patients with AGE caused by pulmonary barotrauma there may be a coexisting pneumothorax, which could develop into tension pneumothorax during chamber decompression. Therefore, if the patient will be treated in a monoplace chamber, placement of a chest tube prior to HBOT is recommended. For multiplace chamber treatment careful monitoring is a feasible option. Coexisting pneumomediastinum does not generally require any specific therapy, and will usually resolve during HBOT.¹
¹ Hyperbaric Oxygen 2003: Indications and Results, The Hyperbaric Oxygen Therapy Committee Report by John J. Feldmeier, D.O., Chairman and Editor. Copyright 2003, Undersea and Hyperbaric Medical Society, Inc., Kensington, MD.