S. Verbanck et al., PULMONARY TISSUE VOLUME, CARDIAC-OUTPUT, AND DIFFUSING-CAPACITY IN SUSTAINED MICROGRAVITY, Journal of applied physiology, 83(3), 1997, pp. 810-816
In microgravity (mu G) humans have marked changes in body fluids, with
a combination of an overall fluid loss and a redistribution of fluids
in the cranial direction. We investigated whether interstitial pulmon
ary edema develops as a result of a headward fluid shift or whether pu
lmonary tissue fluid volume is reduced as a result of the overall loss
of body fluid. We measured pulmonary tissue volume (Vti), capillary b
lood flow and diffusing capacity in four subjects before, during, and
after 10 days of exposure to mu G during space-flight. Measurements we
re made by rebreathing a gas mixture containing small amounts of acety
lene, carbon monoxide, and argon. Measurements made early in flight in
two subjects showed no change in Vti despite large increases in strok
e volume (40%) and diffusing capacity (13%) consistent with increased
pulmonary capillary blood volume. Late inflight measurements in four s
ubjects showed a 25% reduction in Vti compared with preflight controls
(P < 0.001). There was a concomittant reduction in stroke volume, to
the extent that it was no longer significantly different from prefligh
t control. Diffusing capacity remained elevated (11%; P < 0.05) late i
n flight. findings suggest that, despite increased pulmonary perfusion
and pulmonary capillary blood volume, interstitial pulmonary edema do
es not result from exposure to mu G.