Panerai Ronney B, Barnes Sam C, Nath Mintu, Ball Naomi, Robinson Thompson G, Haunton Victoria J
Department of Cardiovascular Sciences, University of Leicester , Leicester , United Kingdom.
National Institute for Health Research, Leicester Biomedical Research Centre, University of Leicester , Leicester , United Kingdom.
Am J Physiol Regul Integr Comp Physiol. 2018 Oct 1;315(4):R730-R740. doi: 10.1152/ajpregu.00010.2018. Epub 2018 Jul 5.
Dynamic cerebral autoregulation (CA), the transient response of cerebral blood flow (CBF) to rapid changes in arterial blood pressure (BP), is usually modeled as a linear mechanism. We tested the hypothesis that dynamic CA can display nonlinear behavior resulting from differential efficiency dependent on the direction of BP changes. Cerebral blood velocity (CBV) (transcranial Doppler), heart rate (HR) (three-lead ECG), continuous BP (Finometer), and end-tidal CO (capnograph) were measured in 10 healthy young subjects during 15 squat-stand maneuvers (SSM) with a frequency of 0.05 Hz. The protocol was repeated with a median (interquartile range) of 44 (35-64) days apart. Dynamic CA was assessed with the autoregulation index (ARI) obtained from CBV step responses estimated with an autoregressive moving-average model. Mean BP, HR, and CBV were different (all P < 0.001) between squat and stand, regardless of visits. ARI showed a strong interaction ( P < 0.001) of SSM with the progression of transients; in general, the mean ARI was higher for the squat phase compared with standing. The changes in ARI were partially explained by concomitant changes in CBV ( P = 0.023) and pulse pressure ( P < 0.001), but there was no evidence that ARI differed between visits ( P = 0.277). These results demonstrate that dynamic CA is dependent on the direction of BP change, but further work is needed to confirm if this finding can be generalized to other physiological conditions and also to assess its dependency on age, sex and pathology.
动态脑自动调节（CA），即脑血流量（CBF）对动脉血压（BP）快速变化的瞬态反应，通常被建模为一种线性机制。我们检验了这样一个假设，即动态CA可能表现出非线性行为，这种行为是由依赖于血压变化方向的不同效率所导致的。在10名健康年轻受试者进行15次频率为0.05Hz的深蹲-站立动作（SSM）过程中，测量了脑血流速度（CBV）（经颅多普勒）、心率（HR）（三导联心电图）、连续血压（Finometer）和呼气末二氧化碳（二氧化碳分析仪）。该方案在间隔中位数（四分位间距）为44（35 - 64）天的情况下重复进行。通过自回归移动平均模型估计的CBV阶跃响应获得的自动调节指数（ARI）来评估动态CA。无论就诊情况如何，深蹲和站立之间的平均血压、心率和CBV均存在差异（均P < 0.001）。ARI显示SSM与瞬态进展之间存在强烈的相互作用（P < 0.001）；一般来说，深蹲阶段的平均ARI高于站立阶段。ARI的变化部分由CBV（P = 0.023）和脉压（P < 0.001）的伴随变化所解释，但没有证据表明不同就诊之间ARI存在差异（P = 0.277）。这些结果表明动态CA依赖于血压变化的方向，但需要进一步的研究来确认这一发现是否可以推广到其他生理状况，以及评估其对年龄、性别和病理状态的依赖性。
