Clinical effects of thigh cuffs during a 7-day 6 degrees head-down bed rest

Thigh cuffs are used by Russian cosmonauts to limit the fluid shift induced by space flight. A ground simulation using the head-down bed rest (HDBR) m odel was performed to assess the effects of thigh cuffs on clinical toleran ce and orthostatic adaptation. 8 male healthy volunteers (32.4 +/-1.9 years ) participated twice in a 7-day HDBR - one time with thigh cuffs (worn dail y from 9 am to 7 pm) (TC) and one time without (WTC). Orthostatic tolerance was assessed by a 10 minute stand test and by a LBNP test (5 min at -15, - 30, -45 mmHg) before (BDC-1) and at the end of the HDBR period (R+1). Plasm a volume was measured before and at the end of HDBR by the Evans blue dye d ilution technique. Thigh cuffs limits headache due to fluid shift, as well as the loss in plasma volume (TC: -5.85 +/-0.95%; WTC: -9.09 +/-0.82%, p <0 .05). The mean duration of the stand test (R+1) did not differ in the two g roup (TC 7.1 +/-1.3 min; WTC 7.0 +/-1.0 min). The increase in HR and decrea se in diastolic blood pressure were slightly but significantly larger witho ut thigh cuffs. Duration of the LBNP tests did not differ with thigh cuffs. Thigh cuffs limit the symptoms due to fluid shift and the loss in plasma v olume. They partly reduced the increase in HR during orthostatic stress but had no effect on duration of orthostatic stress tests. (C) 2001 Published by Elsevier Science Ltd.