Cardiac and humoral changes induced by recreational scuba diving

The aim of this study was to evaluate the prevalence and the possible clini cal relevance of circulating bubbles after a recreational scuba dive. Twent y healthy subjects (18 male, 2 female; age range 25-36 yr) underwent a Dopp ler-echocardiographic study in basal conditions and 1.9 +/- 0.2 h after a r ecreational scuba dive. Venous blood samples were taken just before the two ultrasonic studies to obtain leukocyte and platelet counts and plasma acti vity of angiotensin-converting enzyme (ACE; assumed as pulmonary endothelia l damage marker). Circulating bubbles were observed in the right heart cham bers of 12 subjects after the dive. The echocardiographic and humoral data were evaluated before and after diving in subjects with and without circula ting bubbles. At the postdive evaluation, a significant increase in right v entricular dimensions (37.4 +/- 3.9 vs. 40.7 +/- 4.0 mm; P < 0.01) and a si gnificant reduction of early diastolic filling velocities of both right (59 .1 +/- 16.4 vs. 48.9 +/- 6.9 cm.s(-1); P < 0.05) and left (76.2 +/- 9.9 vs. 67.5 +/- 10.2 cm.s(-1); P < 0.02) ventricle were observed in the group wit h circulating bubbles. In the same group, significant increases in ACE acti vity (92.9 +/- 41.1 vs. 105.9 +/- 41.7 U.liter(-1); P < 0.05), platelets (2 17 +/- 34 vs. 232 +/- 35.10(3).mu l(-1); P < 0.01), and granulocytes (3,704 +/- 715.mu l(-1) vs. 5,212 +/- 1,995.mu l(-1); P < 0.001) were observed. T he bubble-free group showed only a postdive significant decrease of left ve ntricular early diastolic filling velocity (74 +/- 6.8 vs. 62.6 +/- 4.5 cm. s(-1); P < 0.005). These data may indicate that circulating gas bubbles are associated with cardiac changes, suggesting a right ventricular overload a nd an impairment of ventricular diastolic performance. Postdive humoral and hematologic changes are consistent with the hypothesis that "silent" gas b ubbles may damage pulmonary endothelium and activate the reactive systems o f the human body.