INTRODUCTION: Post-spaceflight orthostatic intolerance affects approximately 30% of short-duration and 80% of long-duration crewmembers. While the current NASA antigravity suit is effective during Space Shuttle re-entry, it is not designed to be worn postflight and has several drawbacks. The purpose of this study was to evaluate the use of commercially available, thigh-high, gradient compression garments to prevent post-spaceflight orthostatic intolerance. METHODS: Before spaceflight, five male Shuttle astronauts were fitted for compression garments. Postflight stand time, blood pressure, heart rate, stroke volume, cardiac output, and peripheral resistance during 10-min, 80 degrees head-up tilt test within 4 h of landing in these astronauts were retrospectively compared to a group of nine male astronauts not wearing the compression garments. RESULTS: On landing day, three of nine non-countermeasure astronauts developed presyncopal symptoms and could not complete the test, while no countermeasure subjects became presyncopal. Compared to the non-countermeasure subjects, the countermeasure subjects had higher systolic blood pressure (116 +/- 3 vs. 134 +/- 2 mmHg), stroke volume (42 +/- 5 vs. 57 +/- 6 ml), and cardiac output (3.1 +/- 0.3 vs. 4.6 +/- 0.4 L). Heart rate was not different between groups. CONCLUSIONS: In this small pilot study, the rate of presyncope in the non-countermeasure group was similar to that reported previously in subjects without a compression garment. In contrast, thigh-high graded compression garments mitigated the symptoms of orthostatic intolerance by improving stroke volume, cardiac output, and systolic blood pressure responses to standing.
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