Tiecks F P, Lam A M, Matta B F, Strebel S, Douville C, Newell D W
Department of Anesthesiology, University of Washington School of Medicine, Harborview Medical Center, Seattle 98104, USA.
Stroke. 1995 Aug;26(8):1386-92. doi: 10.1161/01.str.26.8.1386.
Knowledge is limited about the effects of the Valsalva maneuver on cerebral circulation because of the poor temporal resolution of traditional cerebral blood flow measurements. The purpose of this study was to investigate changes in cerebral blood flow during the Valsalva maneuver and to explore its potential use for the evaluation of cerebral autoregulation.
Using transcranial Doppler ultrasonography, we simultaneously recorded systemic arterial blood pressure in the radial artery and flow velocities in both middle cerebral arteries in 10 healthy adults during the Valsalva maneuver. Gosling's pulsatility index was calculated for all phases of the Valsalva maneuver. Autoregulatory capacities were estimated from the change in cerebrovascular resistance (flow velocity in relationship to blood pressure) during phase II and changes in the velocity-pressure relationship in phase IV relative to phase I.
The characteristic changes in blood pressure (phases I to IV) were seen in all subjects, accompanying distinct changes in cerebral blood flow velocity. The relative changes in mean velocity during phases II and IV were significantly greater than those in mean blood pressure. Compared with the baseline value, velocity decreased by 35% in phase IIa, then rose by 56.5% in phase IV (corresponding changes in blood pressure were -10.2% and +29.8%, respectively). During phase II, the pulsatility and cerebrovascular resistance decreased by 19.9%. The increase in cerebral blood flow velocity in phase IV was significantly higher than in phase I (P < .0004), and there was no corresponding significant difference in blood pressure.
These results demonstrated that in healthy humans the Valsalva maneuver causes characteristic changes in systemic blood pressure as well as in flow velocity in the middle cerebral artery, reflecting the sympathetic and cerebral autoregulatory responses, respectively. Analysis of these changes may provide an estimate of autoregulatory capacity.
由于传统脑血流测量的时间分辨率较差，关于瓦尔萨尔瓦动作对脑循环影响的知识有限。本研究的目的是调查瓦尔萨尔瓦动作期间脑血流的变化，并探索其在评估脑自动调节方面的潜在用途。
我们使用经颅多普勒超声，在10名健康成年人进行瓦尔萨尔瓦动作期间，同时记录桡动脉的全身动脉血压和双侧大脑中动脉的血流速度。计算瓦尔萨尔瓦动作各阶段的戈斯林搏动指数。根据第二阶段脑血管阻力（血流速度与血压的关系）的变化以及第四阶段相对于第一阶段的速度 - 压力关系变化来估计自动调节能力。
所有受试者均出现血压的特征性变化（第一阶段至第四阶段），同时脑血流速度也有明显变化。第二阶段和第四阶段平均速度的相对变化显著大于平均血压的相对变化。与基线值相比，第二阶段a期速度下降35%，然后在第四阶段上升56.5%（血压的相应变化分别为 -10.2%和 +29.8%）。在第二阶段，搏动性和脑血管阻力下降了19.9%。第四阶段脑血流速度的增加显著高于第一阶段（P <.0004），而血压无相应的显著差异。
这些结果表明，在健康人体中，瓦尔萨尔瓦动作会导致全身血压以及大脑中动脉血流速度发生特征性变化，分别反映交感神经和脑自动调节反应。对这些变化的分析可能提供自动调节能力的估计。
