First measured inflight on the Skylab 4 crewmembers; leg volume measurements were also performed on the Apollo-Soyuz Test Project (ASTP) crewmembers. The objectives of this study were to substantiate the volume reduction that occurs inflight, to obtain inflight leg volume determinations earlier than those obtained on Skylab 4 and to document the time course of fluid shifts by frequent leg volume measurements.
The earliest inflight determinations were obtained approximately 6 hours into flight. Leg volume decreased 0.26 liters below the preflight volume and was statistically significant. After 32 hours of space flight, all three crewmembers evidenced substantial leg volume reductions of 5 to 10 percent. This decrease was observed earlier than in previous leg volume measurements obtained on Skylab 4 (taken on flight day 3). Subsequent measurements showed moderate variability with a definite downward trend. Most variations were parallel in all three crewmembers, although different crewmembers contributed to measurement variance.
Earliest postflight determinations were taken between 1.5 and 2 hours after splashdown. Leg volumes on all three crewmembers had increased well above their last inflight values. Second measurements taken on recovery day, 2 to 5 hours after splashdown, evidenced even greater leg volumes. This was in accordance with the reversing effects of re-adaption to the 1-G environment. Leg volumes measurements one day after landing were achieved before arising that morning and clearly show the established diurnal pattern of minimal volume at the end of the sleep period, with the subjects in a supine position. The last postflight measurements taken four days after landing exhibited increasing trends toward preflight values. Because of circumstances associated with a problem during landing, leg volumes were not obtained beyond four days after landing.
In conclusion, it appeared that the major fluid volume shift from the legs does not occur within the first few hours in orbit. The trend seems to have assumed an exponential form with maximum decrease within the first 24 hours. A distant plateau was evident by 3 to 5 days inflight, with little significant additional decrease occurring after the first week in weightlessness. These fluid volume shifts coincided with the occurrence of crew symptomatology, such as a feeling of fullness in the face, and the plateau with relative adaptive stability.
|Mission||Launch/Start Date||Landing/End Date||Duration|
|ASTP||07/15/1975||07/24/1975||9 days, 7.5 hours|