Zhang R, Zuckerman J H, Giller C A, Levine B D
Institute for Exercise and Environmental Medicine, Presbyterian Hospital of Dallas, Texas 75231, USA.
Am J Physiol. 1998 Jan;274(1 Pt 2):H233-41. doi: 10.1152/ajpheart.1998.274.1.h233.
To test the hypothesis that spontaneous changes in cerebral blood flow are primarily induced by changes in arterial pressure and that cerebral autoregulation is a frequency-dependent phenomenon, we measured mean arterial pressure in the finger and mean blood flow velocity in the middle cerebral artery (VMCA) during supine rest and acute hypotension induced by thigh cuff deflation in 10 healthy subjects. Transfer function gain, phase, and coherence function between changes in arterial pressure and VMCA were estimated using the Welch method. The impulse response function, calculated as the inverse Fourier transform of this transfer function, enabled the calculation of transient changes in VMCA during acute hypotension, which was compared with the directly measured change in VMCA during thigh cuff deflation. Beat-to-beat changes in VMCA occurred simultaneously with changes in arterial pressure, and the autospectrum of VMCA showed characteristics similar to arterial pressure. Transfer gain increased substantially with increasing frequency from 0.07 to 0.20 Hz in association with a gradual decrease in phase. The coherence function was > 0.5 in the frequency range of 0.07-0.30 Hz and < 0.5 at < 0.07 Hz. Furthermore, the predicted change in VMCA was similar to the measured VMCA during thigh cuff deflation. These data suggest that spontaneous changes in VMCA that occur at the frequency range of 0.07-0.30 Hz are related strongly to changes in arterial pressure and, furthermore, that short-term regulation of cerebral blood flow in response to changes in arterial pressure can be modeled by a transfer function with the quality of a high-pass filter in the frequency range of 0.07-0.30 Hz.
为了验证脑血流量的自发变化主要由动脉压变化引起以及脑自动调节是一种频率依赖性现象这一假设，我们在10名健康受试者仰卧休息以及大腿袖带放气诱导急性低血压期间，测量了手指处的平均动脉压和大脑中动脉的平均血流速度（VMCA）。使用Welch方法估计动脉压变化与VMCA之间的传递函数增益、相位和相干函数。作为该传递函数的傅里叶逆变换计算得到的脉冲响应函数，能够计算急性低血压期间VMCA的瞬态变化，并将其与大腿袖带放气期间直接测量的VMCA变化进行比较。VMCA的逐搏变化与动脉压变化同时发生，并且VMCA的自谱显示出与动脉压相似的特征。随着频率从0.07增加到0.20 Hz，传递增益大幅增加，同时相位逐渐减小。相干函数在0.07 - 0.30 Hz频率范围内> 0.5，在< 0.07 Hz时< 0.5。此外，在大腿袖带放气期间，VMCA的预测变化与测量值相似。这些数据表明，在0.07 - 0.30 Hz频率范围内发生的VMCA自发变化与动脉压变化密切相关，而且，响应动脉压变化的脑血流量短期调节可以通过在0.07 - 0.30 Hz频率范围内具有高通滤波器特性的传递函数来建模。
