Custaud M A, Millet C, Frutoso J, Maillet A, Gauquelin G, Gharib C, Fortrat J O
Laboratoire de Physiologie de l'Environnement, Faculté de Médecine Lyon Grange-Blanche, 8 avenue Rockefeller, 69373 Lyon CEDEX 08, France.
Acta Physiol Scand. 2000 Oct;170(2):77-85. doi: 10.1046/j.1365-201x.2000.00763.x.
Orthostatic intolerance (OI) is the most serious symptom of cardiovascular deconditioning induced by head-down bed rest or weightlessness. Wearing venoconstrictive thigh cuffs is an empirical countermeasure used by Russian cosmonauts to limit the shift of fluid from the lower part of the body to the cardio-cephalic region. Our aim was to determine whether or not thigh cuffs help to prevent orthostatic hypotension induced by head-down bed rest. We studied the effect of thigh cuffs on eight healthy men. The cuffs were worn during the day for 7 days of head-down bed rest. We measured: orthostatic tolerance (stand tests and lower body negative pressure tests), plasma volume (Evans blue dilution), autonomic influences (plasma noradrenaline) and baroreflex sensitivity (spontaneous baroreflex slope). Thigh cuffs limited the loss of plasma volume (thigh cuffs: -201 +/- 37 mL vs. control: -345 +/- 42 mL, P < 0.05), the degree of tachycardia and reduction in the spontaneous baroreflex sensitivity induced by head-down bed rest. However, the impact of thigh cuffs was not sufficient to prevent OI (thigh cuffs: 7.0 min of standing time vs. control: 7.1 min). Decrease in absolute plasma volume and in baroreflex sensitivity are known to be important factors in the aetiology of OI induced by head-down bed rest. However, dealing with these factors, using thigh cuffs for example, is not sufficient to prevent OI. Other factors such as venous compliance, microcirculatory changes, peripheral arterial vasoconstriction and vestibular afferents must also be considered.
直立不耐受（OI）是头低位卧床休息或失重引起的心血管失适应最严重的症状。佩戴静脉收缩性大腿套是俄罗斯宇航员用来限制液体从身体下部向心脑区域转移的一种经验性对策。我们的目的是确定大腿套是否有助于预防头低位卧床休息引起的直立性低血压。我们研究了大腿套对8名健康男性的影响。在头低位卧床休息的7天里，白天佩戴大腿套。我们测量了：直立耐受能力（站立试验和下体负压试验）、血浆容量（伊文思蓝稀释法）、自主神经影响（血浆去甲肾上腺素）和压力反射敏感性（自发性压力反射斜率）。大腿套限制了血浆容量的减少（大腿套组：-201±37 mL，对照组：-345±42 mL，P<0.05）、心动过速程度以及头低位卧床休息引起的自发性压力反射敏感性降低。然而，大腿套的作用不足以预防直立不耐受（大腿套组：站立时间7.0分钟，对照组：7.1分钟）。已知绝对血浆容量和压力反射敏感性降低是头低位卧床休息引起的直立不耐受病因中的重要因素。然而仅处理这些因素，比如使用大腿套，不足以预防直立不耐受。还必须考虑其他因素，如静脉顺应性、微循环变化、外周动脉血管收缩和前庭传入神经。
