The effects of successive air and trimix dives on human cardiovascular function

Abstract

The use of trimix has significantly increased among diver population. However, the data indicating how the field trimix dives at most common depths affect the cardiovascular function are sparse. The purpose of this study was to investigate the cardiovascular effects of trimix dives and compare them with the air dives, as well as determine whether the repetition of dives in successive days affects their extent. Eight professional divers performed four dives in consecutive days where the dive depth was progressively increased to the maximum of 55 m, and the divers used air in the 1st dive, nitrox 25 for the 2nd, and trimix 20/30 for the 3rd and 4th dive. After each dive, a significantly decreased left ventricular ejection fraction and fractional shortening, as well as increased end‐systolic volume without a change in end‐diastolic volume were found, indicating a depressed systolic function of the left heart. Assessment of the ratio between pulmonary artery acceleration time and right ventricular ejection time revealed an increase in PAP after all the dives. The current study shows that the cardiovascular effects of trimix dives do not differ from those of the dives with compressed air. However, it suggests that even a very safe and conservative trimix diving profile exerts significant cardiovascular effects.This study was supported by the Croatian Ministry of Science, Education and Sports.