Dynamic cardiorespiratory interaction during head-up tilt-mediated presyncope.
Dynamic cardiorespiratory interaction during head-up tilt-mediated presyncope.
复制标题
平视倾斜介导的先兆晕厥期间的动态心肺相互作用。
DOI：
10.1152/ajpheart.00485.2004
复制
发表时间：
2004
期刊：
影响因子：
--
通讯作者：
Patwardhan,A
中科院分区：
文献类型：
--
作者：
Krishnamurthy,S;Wang,X;Bhakta,D;Bruce,E;Evans,J;Justice,T;Patwardhan,A
在28名健康成人中，我们比较了两组受试者的呼吸和脑自动调节之间的动态相互作用：在70°被动直立倾斜(HUT)过程中有和没有出现晕厥前症状的受试者，即非晕厥患者(23例)和晕厥前患者(5例)。记录空气流量、二氧化碳、脑血流速度(CBF)、心电图和血压(BP)。为了确定平均血压(MBP)和收缩压(SBP)对晕厥前受试者CBF的影响，估计了这些变量与平均CBF和峰值CBF(CBFm和CBFp)之间的相关性和传递函数。为了确定呼气末二氧化碳(ETCO2)对CBF的影响，计算了相对CO2反应性(ETCO2每毫米汞柱变化中CBFm的变化百分比)。结果发现，在HUT期间出现症状前的突触前期受试者，在呼吸频率段，SBP与CBFp的一致性较高(P=0.02)，BP(MBP与SBP)与CBFm之间的传递函数增益较大(MBP，P=0.01；SBP，P=0.01)。在晕厥前的最后3分钟，晕厥前期患者的相对二氧化碳反应性降低(P=0.005)，这可能是EtCO2下降幅度较大的结果。我们假设，二氧化碳介导的阻力增加减弱了自动调节，从而增强了全身和脑血流动力学之间的关系。我们的结果表明，涉及脑血流动力学的心肺相互作用的改变可能在倾斜过程中的一连串事件中起作用，最终导致不明原因的晕厥。
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° 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 (CBFmand CBFp) were estimated. To determine the influence of end-tidal CO2(ETco2) on CBF, the relative CO2reactivity (%change in CBFmper mmHg change in ETco2) was calculated. We found that in presyncopal subjects before symptoms during HUT, coherence between SBP and CBFpwas higher (P= 0.02) and gains of transfer functions between BP (MBP and SBP) and CBFmwere larger (MBP,P= 0.01; SBP,P= 0.01) in the respiratory frequency region. In the last 3 min before presyncope, presyncopals had a reduced relative CO2reactivity (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.