[Water content of the lungs during 7-day anti-orthostatic hypokinesia]

The time-course variation of the water content of the lungs of seven male volunteers were examined during 7-day head-down tilt (at -15 degrees). As compared to the horizontal subjects, the tilted subjects showed a significant increase in the water content from 557 +/- 19 ml to 612 +/- +/- 63 ml by the 7th hour of the tilt. Later on the parameter gradually declined and on tilt day 7 almost returned to the pretest level, i.e., 567 +/- 46 ml. This increase in the water content during the first hours of the exposure can be attributed to the hydrostatic factors: higher pulmonary artery pressure and higher cardiac output. The increase in the water content on tilt days 3-7 can be associated with changes in the permeability of lung capillaries, drainage function of the lymphatic system of the lungs, and colloidal-osmotic pressure in the perivascular space of the lungs.