Metabolic consequences of garments worn to protect against post-spaceflight orthostatic intolerance.

INTRODUCTION Astronauts have worn an inflatable antigravity suit (AGS) during Space Shuttle re-entry and landing to protect against hypotension and syncope, but ambulation with an inflated AGS requires significant effort and may prevent successful completion of an unaided emergency egress from the vehicle. NASA is considering the use of alternative garments to provide protection against post-spaceflight orthostatic intolerance. The purpose of this study was to compare the metabolic cost of walking in NASA's current AGS with that of walking in a commercially available elastic compression garment (thigh-high stockings), a candidate garment for use after exploration missions. METHODS There were 10 volunteers (5 men, 5 women) who walked on a treadmill at 5.6 km x h(-1) for 5 min, a simulation of unaided egress previously used in our laboratory, in 3 different conditions presented in random order: wearing exercise clothes, wearing elastic compression garments, and wearing the AGS. Oxygen consumption (Vo2), carbon dioxide production (Vco2), and ventilation (V(E)) were compared using repeated-measures ANOVA and Tukey's Honestly Significant Difference test. RESULTS Vo2 while wearing the AGS was 12% greater than when wearing the elastic compression garments and 15% greater than while wearing exercise clothes. There were no differences between the elastic compression garments and exercise clothes only conditions. Vco2 and VE also were greater while walking in the AGS than walking in the elastic compression garments or exercise clothes. CONCLUSIONS Wearing elastic compression garments as a countermeasure to post-spaceflight orthostatic intolerance may not impair unaided egress from a space vehicle.