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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
Objective To observe the changes of blood flow velocity in the middle cerebral artery during 4d head-down bed simulations. Methods Eight healthy male volunteers underwent 4d - 6 ° head-down ambulation test. Bed rest and bed rest at the end of 4d 2 times on the tilt bed endurance test, bed rest (supine position), bed rest days 1, 3, 4, and 2 days after waking with the transcranial Doppler ultrasound measured right Middle cerebral artery blood flow velocity. Results At the end of 4 d (87.5%), the rate of standing endurance was significantly higher than that before bed rest (37.5%) (P <0.05). The systolic blood flow velocity, diastolic blood flow velocity and mean blood flow velocity of middle cerebral artery decreased in the first and third day of bed compared with those before bedtime, but did not reach the significant level, and were significantly decreased on the fourth day of bedridden (P < 0 .0 5), basically recovered after the first 2 days. During bed rest, mean arterial pressure and diastolic pressure were significantly increased (P <0. 05), weight was significantly reduced (P <0. 05). Conclusion 4 d head-lying bed can cause a significant decrease in the velocity of blood flow in the middle cerebral artery and an increase in the incidence of standing stamina. Decreased cerebral blood flow velocity may be one of the mechanisms of poor endurance caused by weightlessness / simulated weightlessness