LEFT-VENTRICULAR GAS EMBOLI IN 6 CASES OF ALTITUDE-INDUCED DECOMPRESSION-SICKNESS

Background: Ultrasonic techniques have demonstrated venous gas emboli (VGE) during exposure to high altitude. VGE per se have not been consi dered clinically hazardous. Arterial gas emboli (AGE), however, are vi ewed with great concern. The crossing-over of venous gas to the arteri al circulation has not previously been seen in human subjects at altit ude. This transfer may occur via either intracardiac defects, pulmonar y shunts, or the pulmonary microcirculation. Methods: A non-invasive u ltrasonic echo imaging Doppler system was used to monitor volunteer hu man subjects for gas emboli simultaneously in the right and left sides of the heart at simulated altitude in a chamber. Subjects found to ha ve gas cross-over were evaluated for septal defects with either transt horacic or transesophageal echocardiography. Results: Previously unrep orted left ventricular gas emboli were observed with echo imaging in s ix subjects at altitude. In all six cases, at the time of AGE onset, t he VGE scores were high from all monitored sites. Three subjects had n o septal defect, another had a small sinus venosus defect, a third had a patent foramen ovate, and one was not available for evaluation. Fiv e of the cases became symptomatic at the time of AGE onset. Conclusion s: Operational altitude exposures known to elicit high VGE counts in t he majority of people should be avoided because of an increased risk o f right-to-left gas cross-over and resulting potential for severe cere bral symptomatology.