Increase of pulmonary arterial pressure in subjects with venous gas emboli after uncomplicated recreational SCUBA diving.

The presence of circulating gas bubbles has been repeatedly reported after uncomplicated SCUBA dives. The clinical and pathophysiological relevance of this phenomenon is still under debate but some experimental data suggest that silent bubbles may have a damaging potential on pulmonary endothelial cells. The aim of the present study was to evaluate the possible hemodynamic effect on pulmonary circulation of post-dive circulating gas bubbles. To this aim, 16 experienced divers were studied by Doppler-echocardiography in basal conditions and 2.0 ± 0.15 h after an uncomplicated, unrestricted recreational SCUBA dive. At the post-dive examination, circulating bubbles were present in 10/16 subjects (62.5%). Divers with circulating bubbles showed a significant post-dive increase of pulmonary systolic arterial pressure (evaluated by the maximal velocity of the physiological tricuspid regurgitation; P < 0.01)) and right ventricular internal dimension (P < 0.05). Divers without circulating bubbles showed no significant change in cardiac anatomy and pulmonary arterial pressure. Both groups showed a significant post-dive decrease of transmitral E/A ratio (index of left ventricular diastolic function: subjects with bubbles P < 0.01; subjects without bubbles P < 0.05). These results seem to indicate that circulating gas bubbles may lead to a hemodynamically relevant increase of pulmonary arterial pressure, able to induce an acute right ventricular dilation. Post-dive diastolic function changes, observed in both groups, may be explained by a preload reduction due to immersion natriuresis. The results of the present study add some evidence that post-dive circulating bubbles, although symptomless, have an easily detectable pathogenetic potential, inducing unfavorable hemodynamic changes in the lesser circulation.