Abstract
Aim: This study assessed hemodynamic changes and myocardial function after prolonged dynamic cold water immersions with hyperbaric hyperoxic exposure. Methods: Trained military divers were studied during 8-hour (6 subjects) and 12-hour (6 subjects) dives in a hyperbaric chamber (1.7 and 3 bar) in 18°C water. Subjects were breathing hyperoxic gas (100% oxygen or up to 1.7 bar PO2) and performed bouts of physical exercise. Conventional and speckle tracking transthoracic echocardiography (TTE) were performed before, immediately after, and 15 hours after dives. Results: We observed a decrease in left and right ventricular preloads, and lowered stroke volume immediately after dives. These parameters remained below baseline values 15h after dive termination. These changes were not significantly different between 8h and 12h dives. Speckle tracking analysis showed altered function of the left and right ventricles reflected by a transient decrease in ventricular parameters as measured by echography in the hour immediately after the end of immersion (table). Conclusion: Hemodynamic changes and transient alterations in strain and strain rate myocardial parameters were assessed immediately after 8 to 12 h dives. Immersion-linked changes in blood volume were likely involved in lowering cardiac preload and stroke volume. Altered ventricular strain and strain rates could be the result of lowered blood volume, hyperoxic breathing and increased cardiac pre- and after-load.
Published Version
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