Effect of simulated dives on diastolic function in healthy men

Scuba diving may elicit acute changes to human cardiovascular function. Environmental stresses such as immersion, cold, and venous gas microbubbles all have been shown to contribute to right ventricular overload and impaired left ventricular filling after single dives. We investigated cardiac function after simulated dry chamber dives. Twenty male divers [mean age 31 years, standard deviation (SD) 8 years, mean body mass index 26 kgm⁻² (SD 3 kgm⁻²)] participated in the study. All subjects had normal ECG, stress-ECG, and transthoracic echocardiography at rest. Echocardiographic assessment of diastolic function [E/A-ratio, deceleration time (DT), isovolumic relaxation time (IVRT), E/e′-ratio] was performed directly prior to and 20 and 80 min after two simulated dry hyperbaric chamber dives (maximal pressure 600 kPa, duration 60 min) that were conducted within 1 week. DT statistically significantly decreased from 163 ms (SD 14 ms) to 125 ms (SD 15 ms) 20 min after the dive (p < 0.0001), whereas 80 min after decompression these changes tended to return to baseline [146 ms (SD 14 ms); p = 0.06]. There was no statistically significant change in heart rate, E/A-ratio or E/e′-ratio after 20 or 80 min compared to baseline. These changes could be reproduced after the second dry chamber dive. No gas microbubbles were detectable during or after decompression from either dive. Simulated hyperbaric dry chamber dives were associated with a transient decrease in deceleration time in healthy men. Factors other than immersion, cold, or nitrogen microbubbles may contribute to acute changes in cardiac function after single scuba dives.