VENOCONSTRICTIVE THIGH CUFFS IMPEDE FLUID SHIFTS DURING SIMULATED MICROGRAVITY

Background: This study determined the efficacy of venoconstrictive thi gh cuffs, inflated to 50 mmHg, on impeding fluid redistributions durin g simulated microgravity. Methods: There were 10 healthy male subjects who were exposed to a 2-h tilt protocol which started in the standing position, and was followed by 30 min supine, 30 min standing, 30 min supine, 30 min of -12 degrees head down tilt (HDT, to simulate microgr avity), 15 min of HDT with venoconstrictive thigh cuffs inflated, a fu rther 10 min of HDT, 5 min supine, and 10 min standing. To increase th e sensitivity of the techniques in an Earth-based model, 12 degrees HD T was used to simulate microgravity effects on body fluid shifts. Volu me changes were measured with anthropometric sleeve plethysmography. R esults: Transition to the various tilt positions resulted in concomita nt decrements in leg volume (Stand [STD] to Supine [SUP], -3.0%; SUP t o HDT, -2.0%). inflation of the venoconstrictive thigh cuffs to 50 mmH g, during simulated microgravity, resulted in a significant 3.0% incre ase in leg volume from that seen in HDT (p < 0.01). No significant cha nges in systemic cardiovascular parameters were noted during cuff infl ation. Conclusions: We conclude that venoconstrictive thigh cuffs, inf lated to 50 mmHg for 15 min during 12 degrees HDT, can create a more E arth-like fluid distribution. Cuffs could potentially be used to ameli orate the symptoms of cephalad edema seen with space adaptation syndro me and to potentiate existing fluid volume countermeasure protocols.