Cardiovascular Responses to Standing with and without Lower Body Compression Garments after Long-Duration Spaceflight.

Abstract

Long-duration astronauts (>4 months on the International Space Station, 87 total person-missions) participated in an orthostatic test consisting of 2 minutes of prone rest followed by 3.5 minutes of standing preflight, within hours of landing on the first day of recovery (R+0), and 1, 3, 7, 14, and 30 days after landing. Astronauts and cosmonauts performed exercise during spaceflight and fluid loading before landing to mitigate cardiovascular deconditioning. On R+0, astronauts participated in testing without compression garments or while wearing 1 of 3 garments designed to prevent orthostatic intolerance: Russian Kentavr, National Aeronautics and Space Administration's gradient compression garment (GCG), or SpaceX's gradient orthostatic protection garment (OPG). On R+0, the change in mean arterial pressure (ΔMAP) from prone to standing tended to decrease without compression garments (-8 mmHg, p=.053) and was less in astronauts wearing the Kentavr (-5 mmHg, p=.02), but not in crewmembers wearing the GCG or OPG. The heart rate response from prone to standing (ΔHR) on R+0 tended to increase in those not wearing compression garments (+11 bpm, p=.051) and was greater when wearing the Kentavr (+9 bpm, p<.0001) or the OPG (+10 bpm, p=.003), but not different in those wearing the GCG (+1 bpm, p=0.74). Although ΔHR when not wearing compression garments was greater (p<.05) for at least 2 weeks after landing, ΔMAP was not different from preflight. Wearing NASA's GCG mitigates cardiovascular stress during standing after long-duration spaceflight, and full recovery of orthostatic responses to standing without compression garments is not complete for weeks.