Aaslid R, Lindegaard K F, Sorteberg W, Nornes H
Institute of Applied Physiology and Medicine, Seattle, Washington.
Stroke. 1989 Jan;20(1):45-52. doi: 10.1161/01.str.20.1.45.
We studied the response of cerebral blood flow to acute step decreases in arterial blood pressure noninvasively and nonpharmacologically in 10 normal volunteers during normocapnia, hypocapnia, and hypercapnia. The step (approximately 20 mm Hg) was induced by rapidly deflating thigh blood pressure cuffs following a 2-minute inflation above systolic blood pressure. Instantaneous arterial blood pressure was measured by a new servo-cuff method, and cerebral blood flow changes were assessed by transcranial Doppler recording of middle cerebral artery blood flow velocity. In hypocapnia, full restoration of blood flow to the pretest level was seen as early as 4.1 seconds after the step decrease in blood pressure, while the response was slower in normocapnia and hypercapnia. The time course of cerebrovascular resistance was calculated from blood pressure and blood flow recordings, and rate of regulation was determined as the normalized change in cerebrovascular resistance per second during 2.5 seconds just after the step decrease in blood pressure. The reference for normalization was the calculated change in cerebrovascular resistance that would have nullified the effects of the step decrease in arterial blood pressure on cerebral blood flow. The rate of regulation was 0.38, 0.20, and 0.11/sec in hypocapnia, normocapnia, and hypercapnia, respectively. There was a highly significant inverse relation between rate of regulation and PaCO2 (p less than 0.001), indicating that the response rate of cerebral autoregulation in awake normal humans is profoundly dependent on vascular tone.
我们在10名正常志愿者处于正常碳酸血症、低碳酸血症和高碳酸血症状态时，采用非侵入性且非药物性的方法，研究了脑血流量对动脉血压急性阶梯式下降的反应。通过在高于收缩压水平充气2分钟后迅速放气大腿血压袖带，诱导出约20毫米汞柱的血压阶梯式下降。采用一种新的伺服袖带法测量瞬时动脉血压，并通过经颅多普勒记录大脑中动脉血流速度来评估脑血流量的变化。在低碳酸血症状态下，血压阶梯式下降后最早在4.1秒时血流量就完全恢复到测试前水平，而在正常碳酸血症和高碳酸血症状态下反应则较慢。根据血压和血流记录计算脑血管阻力的时间进程，并将调节速率确定为血压阶梯式下降后2.5秒内每秒脑血管阻力的标准化变化。标准化的参考值是为抵消动脉血压阶梯式下降对脑血流量的影响而计算出的脑血管阻力变化。低碳酸血症、正常碳酸血症和高碳酸血症状态下的调节速率分别为0.38、0.20和0.11/秒。调节速率与动脉血二氧化碳分压（PaCO2）之间存在高度显著的负相关（p小于0.001），表明清醒正常人的脑自动调节反应速率严重依赖于血管张力。
