Oxygen divers undergo environmental stressors such as immersion, ventilation with scuba, cold exposure, and increased ambient pressure. All of these stressors may be responsible for acute hemodynamic modifications. We hypothesized that repeated hyperbaric hyperoxia exposure induces long-term cardiovascular modifications. A Doppler echocardiography was conducted on 20 military oxygen divers (average 12 yr diving experience) and compared with 22 controls. Parameters known to be modified by acute hyperoxic exposure, such as left ventricular (LV) function (systolic and diastolic) and arterial compliance, were analyzed. Controls and divers were matched appropriately for age and height, although the divers had a higher body mass index and aerobic capacity. Left atrial and left ventricular diameters did not differ between the two groups. On the other hand, left ventricular mass was significantly higher in the elite military divers (209 +/- 43 g) in comparison with the control group (172 +/- 48 g), even when LV mass was indexed to body surface area. Left ventricular systolic and diastolic function indices, stroke volume, cardiac index, peripheral vascular resistance, and systemic compliance were comparable between the two groups. A greater LV mass was observed in oxygen military divers. The echocardiographic differences between divers and controls could be attributed to the high level physical training undertaken by the military divers. Some stressors, such as cold water immersion, repeated hyperoxic exposures, scuba breathing, and long distance swimming, could have participated to the echocardiographic findings in oxygen divers.
Boussuges, Riera, Rossi, Blatteau, Castagna, Galland, , , (2007). Echocardiography in military oxygen divers. Aviation, space, and environmental medicine, 2007 May;78(5):500-4. https://www.ncbi.nlm.nih.gov/pubmed/17539444