The impact of consecutive freshwater trimix dives at altitude on human cardiovascular function

Abstract

Self-contained underwater breathing apparatus (SCUBA) diving is regularly associated with numerous asymptomatic changes in cardiovascular function. Freshwater SCUBA diving presents unique challenges compared with open sea diving related to differences in water density and the potential for dive locations at altitude. The aim of this study was to evaluate the impact of freshwater trimix diving at altitude on human cardiovascular function. Ten divers performed two dives in consecutive days at 294 m altitude with the surface interval of 24 h. Both dives were at a depth of 45 m with total dive time 29 and 26 min for the first and second dive, respectively. Assessment of venous gas embolization, hydration status, cardiac function and arterial stiffness was performed. Production of venous gas emboli was low, and there were no significant differences between the dives. After the first dive, diastolic blood pressure was significantly reduced, which persisted up to 24 h. Left ventricular stroke volume decreased, and heart rate increased after both dives. Pulse wave velocity was unchanged following the dives. However, the central and peripheral augmentation index became more negative after both dives, indicating reduced wave reflection. Ejection duration and round trip travel time were prolonged 24 h after the first dive, suggesting longer-lasting suppression of cardiac and endothelial function. This study shows that freshwater trimix dives with conservative profiles and low venous gas bubble loads can result in multiple asymptomatic acute cardiovascular changes some of which were present up to 24 h after dive.

Highs and lows of hyperoxia: physiological, performance, and clinical aspects

“…In very high concentrations, oxygen can also show toxic effects on the central nervous system (leading to generalized tonic-clonic convulsions that may result in drowning). At depth, water temperature, physical activity while swimming, and psychological stress of being in an unnatural environment also contribute to cardiovascular alterations (165,270). While ascending, the solubility of the gases decreases as pressure reduces, and the gases come out of solution, appearing as gas bubbles in the circulation.…”

Elevations in Intra-cranial blood flow velocities following a SCUBA Dive and the Influence of Post-dive Exercise

“…Diving with self-contained underwater breathing apparatus (SCUBA) is major physiological stress despite the common participation of recreational, industry and military personnel. For example, the impact of temperature, pressure, increased work of breathing, hyperoxia and psychological stress all have detrimental physiological consequences [22,25,35,42]. Following single or repetitive dives, impairment has been reported in systemic endothelial function [8,26,31], as well as cardiac and autonomic function [5,10,15].…”