4d头低位卧床期间脑血流速度的改变

目的观察 4d头低位卧床模拟失重期间大脑中动脉血流速度的变化。方法 8名健康男性志愿者进行 4d - 6°头低位卧床试验。卧床前和卧床 4d结束时在倾斜床上进行 2次立位耐力检查 ,卧床前(卧位 )、卧床第 1、3、4天及起床后第 2天用经颅多普勒超声仪测量右侧大脑中动脉血流速度。结果 4d卧床结束时 ( 87.5 % )被试者立位耐力不良发生率较卧床前 ( 37.5 % )显著增加 (P <0 .0 5 )。大脑中动脉收缩期血流速度、舒张期血流速度和平均血流速度在卧床第 1、3天较卧床前均有降低趋势 ,但未达到显著水平 ,卧床第 4天均显著降低 (P <0 .0 5 ) ,起床后第 2天基本恢复。在卧床期间 ,平均动脉压及舒张压均显著升高 (P <0 .0 5 ) ,体重显著降低 (P <0 .0 5 )。结论 4d头低位卧床可引起大脑中动脉血流速度显著降低 ,立位耐力不良发生率增加。脑血流速度降低可能是失重 /模拟失重致立位耐力不良的机制之一

Change of Cerebral Blood Flow Velocity during 4 d Head-down Tilt Bed Rest

Objective. To investigate the change of cerebral blood flow velocity during 4 d head-down tilt (HDT) bed rest in humans. Method. Eight healthy male volunteers were exposed to -6 degrees HDT bed rest for 4 d. Orthostatic tolerance was assessed by means of standard tilt test. Cerebral blood flow velocity in the right middle cerebral artery was measured by transcranial Doppler sonography before HDT (supine), on days 1, 3 and 4 of HDT and on day 2 post HDT. Result. After 4 d HDT, the frequency of orthostatic intolerance was significantly higher than those before HDT (P<0.05). The systolic, diastolic and mean blood velocities in the middle cerebral artery tended to decrease on days 1 and 3 of HDT, and decreased significantly on day 4 of HDT, compared with pre-HDT, and returned to basal levels on day 2 post HDT. The mean arterial blood pressure and diastolic blood pressure increased significantly, while the body weight decreased significantly during HDT. Conclusion. It is suggested that 4 d HDT may decrease cerebral blood flow velocity and increase the frequency of orthostatic intolerance. This decrease of cerebral blood flow velocity may be partially responsible for the increased risk of orthostatic intolerance.