Department of Cardiovascular Sciences, University of Leicester, Leicester, United Kingdom.
Physiol Meas. 2017 Nov 30;38(12):2164-2175. doi: 10.1088/1361-6579/aa9086.
Previous studies on cerebral autoregulation have shown the existence of hemispheric symmetry, which may be altered in stroke and traumatic brain injury. There is a paucity of data however on whether the response is symmetrical between those disturbances that cause cerebral hyperperfusion, to those that cause hypoperfusion. Our aim was to investigate whether the responses of cerebral autoregulation to haemodynamic stimuli of different directions are symmetrical.
Using a previously described assessment method, we employed coherent averaging of the cerebral blood flow velocity (CBFV) responses to thigh cuff inflation and deflation, as driven by pseudorandom binary sequences, whilst simultaneously altering the inspired CO. The symmetry of the autoregulatory response was assessed with regards to two parameters, its speed and gain. Using the first harmonic method, critical closing pressure (CrCP) and resistance area product (RAP) were estimated, and the gain of the autoregulatory response was calculated by performing linear regression between the coherent averages of arterial blood pressure (ABP) and CBFV, ABP and CrCP and finally ABP and RAP. A two-way repeated measures ANOVA was used to assess for the effect of the direction of change in ABP and the method of CO administration.
Our results suggest that whilst the direction of ABP change does not have a significant effect, the effect of CO administration method is highly significant (p < 10).
This is the first report to demonstrate the symmetry of the autoregulatory response to stimuli of different directions as well as the short term dynamics of RAP and CrCP under intermittent and constant hypercapnia. As haemodynamic stimulus direction does not appear to have an influence, our findings validate previous work done using different assessment methods.
先前关于脑自动调节的研究表明存在半球对称性，这种对称性可能在中风和创伤性脑损伤中发生改变。然而，关于导致脑过度灌注和灌注不足的两种不同类型的血流动力学刺激，其脑自动调节反应是否对称，目前数据较少。我们的目的是研究脑自动调节对不同方向血流动力学刺激的反应是否对称。
使用先前描述的评估方法，我们采用伪随机二进制序列驱动的大腿袖带充气和放气时脑血流速度（CBFV）的相干平均，同时改变吸入 CO。通过评估两个参数（其速度和增益）来评估自动调节反应的对称性。使用第一谐波方法，估计临界关闭压力（CrCP）和阻力面积产物（RAP），并通过在动脉血压（ABP）和 CBFV、ABP 和 CrCP 以及最终 ABP 和 RAP 的相干平均值之间进行线性回归来计算自动调节反应的增益。采用双向重复测量方差分析评估 ABP 变化方向和 CO 给药方式的影响。
我们的结果表明，虽然 ABP 变化方向没有显著影响，但 CO 给药方式的影响非常显著（p < 10）。
这是第一个报告，证明了自动调节反应对不同方向刺激的对称性，以及在间歇性和恒常性高碳酸血症下 RAP 和 CrCP 的短期动力学。由于血流动力学刺激方向似乎没有影响，我们的发现验证了先前使用不同评估方法进行的工作。
