Body fluid distribution: implications for zero gravity.

M A N N E D SPACE flight is now a reality and data is available regarding the physiologic effects of short periods of weightlessness. 1 The results of our initial manned orbital space flights indicate that although certain phys io log ica l changes do occur during relatively short exposures to weightlessness, such changes have not been of operational significance and have been of a rather minor nature. This lack of gross physiologic alteration was not unexpected as such pioneer experiments as the rocket studies of J. P. Henry in the late 1940's showed that in sedated monkeys exposure to weighdessness for periods of approximately 2 minutes produced no significant changes in arterial or venous blood pressure or heart rate. 2 However, the minor changes which have been observed in recent flights pose some intriguing questions concerning etiology and indicate some rather fertile areas for future research. It seems reasonable to consider that in a zero gravity environment significant alteration of certain gravity conditioned biologic systems will occur as predicted by Gauer and Haber in 1948 s and inferred by Graveline, et al, from studies of human decon-