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首页> 外文期刊>American Journal of Physiology >Dynamic cardiorespiratory interaction during head-up tilt-mediated presyncope.
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Dynamic cardiorespiratory interaction during head-up tilt-mediated presyncope.

机译：抬头倾斜介导的晕厥前的动态心肺相互作用。

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摘要

In 28 healthy adults, we compared the dynamic interaction between respiration and cerebral autoregulation in 2 groups of subjects: those who did and did not develop presyncopal symptoms during 70 degrees passive head-up tilt (HUT), i.e., nonpresyncopal (23 subjects) and presyncopal (5 subjects). Airflow, CO2, cerebral blood flow velocity (CBF), ECG, and blood pressure (BP) were recorded. To determine whether influences of mean BP (MBP) and systolic SP (SBP) on CBF were altered in presyncopal subjects, coherencies and transfer functions between these variables and mean and peak CBF (CBFm and CBFp) were estimated. To determine the influence of end-tidal CO2 (ETco2) on CBF, the relative CO2 reactivity (%change in CBFm per mmHg change in ETco2) was calculated. We found that in presyncopal subjects before symptoms during HUT, coherence between SBP and CBFp was higher (P=0.02) and gains of transfer functions between BP (MBP and SBP) and CBFm were larger (MBP, P=0.01; SBP, P=0.01) in the respiratory frequencyregion. In the last 3 min before presyncope, presyncopals had a reduced relative CO2 reactivity (P=0.005), likely a consequence of the larger decrease in ETco2. We hypothesize that the CO2-mediated increase in resistance attenuates autoregulation such that the relationship between systemic and cerebral hemodynamics is enhanced. Our results suggest that an altered cardiorespiratory interaction involving cerebral hemodynamics may contribute in the cascade of events during tilt that culminate in unexplained syncope.
机译：在28位健康的成年人中，我们比较了两组受试者的呼吸与大脑自动调节之间的动态相互作用：在70度被动抬头向上倾斜（HUT）期间出现和未出现晕厥前症状的受试者，即非晕厥（23名受试者）和晕厥前（5门科目）。记录气流，CO2，脑血流速度（CBF），ECG和血压（BP）。为了确定在晕厥前受试者中平均BP（MBP）和收缩期SP（SBP）对CBF的影响是否发生了改变，估计了这些变量与平均和峰值CBF（CBFm和CBFp）之间的相干性和传递函数。为了确定潮气末CO2（ETco2）对CBF的影响，计算了相对CO2反应性（相对于ETco2的每mmHg变化，CBFm的变化百分比）。我们发现在晕厥前的受试者在HUT出现症状之前，SBP和CBFp之间的相关性较高（P = 0.02），并且BP（MBP和SBP）和CBFm之间的传递函数增益较大（MBP，P = 0.01; SBP，P = 0.01）在呼吸频率区域。在晕厥前的最后3分钟内，晕厥前的相对CO2反应性降低（P = 0.005），这可能是ETco2降低幅度更大的结果。我们假设CO2介导的抗性增加减弱了自动调节，从而增强了全身和脑部血流动力学之间的关系。我们的研究结果表明，涉及脑血流动力学的心肺交互作用改变可能导致倾斜期间的事件级联，最终导致无法解释的晕厥。

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