Seven-day dry immersion: Interrelationship between the changes in the water-electrolyte balance and cardiovascular responses

The results of an experiment with a seven-day dry immersion are presented. Eight healthy men were examined before, during, and after the exposure. It was shown that the primary response involved hemodynamic and water-electrolyte changes. The mechanisms of cardiovascular adaptation to the immersion conditions were revealed. In particular, some electrophysiological shifts in the propagation of myocardial excitation were found, leading to an increase in the variance of natural small oscillations of the electric potential of the heart. The revealed significant reduction of the functional reserves of the cardiovascular regulatory mechanisms during adaptation to dry immersion is of great practical importance. The results suggest that the water-electrolyte balance shifts induced by dry immersion are the basis and the first phase of further changes in the autonomic regulation and functional state of the myocardium.