Mukli Peter, Nagy Zoltan, Racz Frigyes Samuel, Portoro Istvan, Hartmann Andras, Stylianou Orestis, Debreczeni Robert, Bereczki Daniel, Eke Andras
Department of Physiology, Semmelweis University, Budapest, Hungary.
Vascular Cognitive Impairment and Neurodegeneration Program, Oklahoma Center for Geroscience and Healthy Brain Aging, Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, United States.
Front Physiol. 2021 Mar 2;12:622569. doi: 10.3389/fphys.2021.622569. eCollection 2021.
Dynamic interdependencies within and between physiological systems and subsystems are key for homeostatic mechanisms to establish an optimal state of the organism. These interactions mediate regulatory responses elicited by various perturbations, such as the high-pressure baroreflex and cerebral autoregulation, alleviating the impact of orthostatic stress on cerebral hemodynamics and oxygenation. The aim of this study was to evaluate the responsiveness of the cardiorespiratory-cerebrovascular networks by capturing linear and nonlinear interdependencies to postural changes. Ten young healthy adults participated in our study. Non-invasive measurements of arterial blood pressure (from that cardiac cycle durations were derived), breath-to-breath interval, cerebral blood flow velocity (BFV, recorded by transcranial Doppler sonography), and cerebral hemodynamics (HbT, total hemoglobin content monitored by near-infrared spectroscopy) were performed for 30-min in resting state, followed by a 1-min stand-up and a 1-min sit-down period. During preprocessing, noise was filtered and the contribution of arterial blood pressure was regressed from BFV and HbT signals. Cardiorespiratory-cerebrovascular networks were reconstructed by computing pair-wise Pearson-correlation or mutual information between the resampled signals to capture their linear and/or nonlinear interdependencies, respectively. The interdependencies between cardiac, respiratory, and cerebrovascular dynamics showed a marked weakening after standing up persisting throughout the sit-down period, which could mainly be attributed to strikingly attenuated nonlinear coupling. To summarize, we found that postural changes induced topological changes in the cardiorespiratory-cerebrovascular network. The dissolution of nonlinear networks suggests that the complexity of key homeostatic mechanisms maintaining cerebral hemodynamics and oxygenation is indeed sensitive to physiological perturbations such as orthostatic stress.
生理系统及子系统内部和之间的动态相互依存关系是体内平衡机制建立机体最佳状态的关键。这些相互作用介导了由各种扰动引发的调节反应，如高压压力反射和脑自动调节，减轻了直立位应激对脑血流动力学和氧合的影响。本研究的目的是通过捕捉线性和非线性相互依存关系来评估心肺-脑血管网络对姿势变化的反应性。十名年轻健康成年人参与了我们的研究。在静息状态下对动脉血压（由此得出心动周期持续时间）、逐次呼吸间隔、脑血流速度（经颅多普勒超声记录的BFV）和脑血流动力学（HbT，近红外光谱监测的总血红蛋白含量）进行了30分钟的无创测量，随后是1分钟的站立期和1分钟的坐下期。在预处理过程中，对噪声进行了滤波，并从BFV和HbT信号中回归了动脉血压的贡献。通过计算重采样信号之间的成对皮尔逊相关性或互信息来重建心肺-脑血管网络，以分别捕捉它们的线性和/或非线性相互依存关系。心脏、呼吸和脑血管动力学之间的相互依存关系在站立后明显减弱，并在整个坐下期持续存在，这主要可归因于显著减弱的非线性耦合。总之，我们发现姿势变化会引起心肺-脑血管网络的拓扑变化。非线性网络的解体表明，维持脑血流动力学和氧合的关键体内平衡机制的复杂性确实对诸如直立位应激等生理扰动敏感。
