Delayed-Onset Arterial Gas Embolism After Underwater Egress Training

Arterial gas embolism (AGE) may occur while breathing compressed air and failing to exhale during ascent to compensate for gas expansion as pressure decreases. Trauma to the lungs from over-pressurization may result in air bubbles entering the pulmonary veins and subsequently the systemic circulation, causing obstructed blood flow and inflammatory cascades. AGEs are known to always manifest within 10 min of surfacing from depth. In underwater egress training (UET), which is mandatory for U.S. Marines, service members learn to escape from a tilt-wing or rotor aircraft after it submerges and inverts in water.

We report a case of cerebral AGE in which the victim experienced neurological symptoms more than 1 h after completing UET at a depth between only 3.28-6.56 ft (1-2 m). The patient was treated with a U.S. Navy Treatment Table 6 and experienced complete resolution of symptoms.

This case is one of only two AGEs reported with symptom onset occurring after 10 min of surfacing from depth to be published. AGE at depths between 1-2 m has only been reported on three other occasions, and dysbarism injuries during UET are also exceedingly rare. This case demonstrates a situation in which all three events occurred, highlighting the need for increased awareness and clinical consideration of delayed AGE in similar scenarios despite the commonly held belief that AGEs do not occur outside of 10 min of surfacing. Harvey SE, Reynolds RP, Fisher JF. Delayed-onset arterial gas embolism after underwater egress training. Aerosp Med Hum Perform. 2024; 95(11):867-870.