Cardiovascular Systems Laboratory, Dept. of Surgery and Anesthesia, Univ. of Otago, Wellington South, New Zealand.
J Appl Physiol (1985). 2011 Apr;110(4):917-25. doi: 10.1152/japplphysiol.01407.2010. Epub 2011 Feb 3.
The Windkessel properties of the vasculature are known to play a significant role in buffering arterial pulsations, but their potential importance in dampening low-frequency fluctuations in cerebral blood flow has not been clearly examined. In this study, we quantitatively assessed the contribution of arterial Windkessel (peripheral compliance and resistance) in the dynamic cerebral blood flow response to relatively large and acute changes in blood pressure. Middle cerebral artery flow velocity (MCA(V); transcranial Doppler) and arterial blood pressure were recorded from 14 healthy subjects. Low-pass-filtered pressure-flow responses (<0.15 Hz) during transient hypertension (intravenous phenylephrine) and hypotension (intravenous sodium nitroprusside) were fitted to a two-element Windkessel model. The Windkessel model was found to provide a superior goodness of fit to the MCA(V) responses during both hypertension and hypotension (R² = 0.89 ± 0.03 and 0.85 ± 0.05, respectively), with a significant improvement in adjusted coefficients of determination (P < 0.005) compared with the single-resistance model (R² = 0.62 ± 0.06 and 0.61 ± 0.08, respectively). No differences were found between the two interventions in the Windkessel capacitive and resistive gains, suggesting similar vascular properties during pressure rise and fall episodes. The results highlight that low-frequency cerebral hemodynamic responses to transient hypertension and hypotension may include a significant contribution from the mechanical properties of vasculature and, thus, cannot solely be attributed to the active control of vascular tone by cerebral autoregulation. The arterial Windkessel should be regarded as an important element of dynamic cerebral blood flow modulation during large and acute blood pressure perturbation.
血管的风箱特性被认为在缓冲动脉脉动方面起着重要作用，但它们在阻尼脑血流低频波动方面的潜在重要性尚未得到明确检验。在这项研究中，我们定量评估了动脉风箱（外周顺应性和阻力）对相对较大和急性血压变化引起的动态脑血流反应的贡献。从 14 名健康受试者中记录大脑中动脉血流速度（MCA(V)；经颅多普勒）和动脉血压。在短暂性高血压（静脉注射苯肾上腺素）和低血压（静脉注射硝普钠）期间，对低于 0.15 Hz 的压力-流量响应进行低通滤波，并使用双元素风箱模型对其进行拟合。结果发现，风箱模型对高血压和低血压期间的 MCA(V)响应提供了更好的拟合优度（R²=0.89±0.03 和 0.85±0.05，分别），与单阻力模型相比，调整后的确定系数有显著提高（P＜0.005）（R²=0.62±0.06 和 0.61±0.08，分别）。两种干预措施之间在风箱电容和电阻增益方面没有差异，这表明在血压升高和下降期间血管特性相似。结果表明，短暂性高血压和低血压对低频脑血流动力学的反应可能包括血管机械特性的重要贡献，因此不能仅仅归因于脑血管自动调节对血管张力的主动控制。动脉风箱应被视为在大而急性血压扰动期间动态脑血流调节的重要因素。
