Functioning of the kidneys and human body fluids during five-day immersion

Renal function and body composition, including fluids, were studied during space flight conditions imitation with five-day dry immersion in 14 apparently healthy men. Noninvasive research of water spaces of the body was performed using methods of bioimpedance analysis (BIA). It was shown that renal excretion of fluids increased and negative aqueous balance developed during dry immersion. Bioimpedance research revealed decreased volume of the total body and the extracellular fluids, and the amount of circulating plasma also decreased. Thus, under the conditions of immersion, hypohydration developed in the body. In the recovery period, these changes in the hydration level rapidly returned to the initial values. The lean body mass during immersion was reduced insignificantly and the amount of fat, in contrast, exceeded the baseline levels. Furthermore, the experiment showed technical impossibility to obtain reliable impedancemetry data under the dry immersion conditions. © 2014, Pleiades Publishing, Inc.