Aa. Pilmanis et al., LEFT-VENTRICULAR GAS EMBOLI IN 6 CASES OF ALTITUDE-INDUCED DECOMPRESSION-SICKNESS, Aviation, space, and environmental medicine, 67(11), 1996, pp. 1092-1096
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.