Control Criteria of Cardiovascular System Generating 1/f Fluctuations

在这项研究中，我们探索了心血管系统产生1/f波动的控制标准。通过对压力反射增益(BRG)的估计，研究了监管系统的状态依赖性。在从血压(BP)到心率(HR)的开环假设下构建的序列方法估计BRG。因此，估计的BRSS依次为站立、非快速眼动(Non REM)睡眠、REM睡眠、仰卧。另外，在仰卧位立位应力作用下，BRS随倾斜角度(重力)的增大而减小。作为一种新的基于闭环假设的BRS估计方法，提出了一种将序列方法应用于由新息过程驱动的已辨识多元自回归(MAR)模型生成的时间序列的新方法，暂称为“新息法”。序列方法和新息方法得到的估计值之间的比较没有S…更重要的是差距有多大，这消除了开环和闭环技术估计的BRS绝对值的差异。此外，随着立位应力的增加，从血压到血压的闭环脉冲反应加快。类似的分析也适用于脊柱损伤患者的数据。结果表明，高位损伤患者的心血管系统反应不稳定。相比之下，轻度损伤的患者与健康受试者有相似的特征。此外，患者还表现出明显的0.05赫兹振荡，这可能为Mayer波的产生机制提供新的信息。从BP和HR之间的相互依存性分析来看，由于受伤导致它们之间的脱节，心血管系统被认为是不稳定的。由于对立位应激的反应反映了对外周阻力和静脉回流行为的控制，因此可以通过对它们的建模来探索心血管系统的控制标准。此外，我们还构建了以心率和交感神经活动为控制变量，以血压为控制变量的心血管模型。对该模型的最优控制仿真表明，HR产生1/f波动的标准是允许一定偏差的宽松标准，而不是不允许波动的刚性标准。较少

In this study, we explored the control criteria of the cardiovascular system generating 1/f fluctuations. Through estimating the baroreflex gain (BRG), state-dependency of the regulatory system was studied. BRG was estimated by the sequence method constructed under an open-loop assumption from blood pressure (BP) to heart rate (HR). As a result, the estimated BRSs were lower in order standing, non rapid eye movement (nonREM) sleep, REM sleep, supine. In addition, under the head-up tilting posing orthostatic stress, it was paradoxically found that BRS becomes reduced as the tilt angle (gravity) increases. As a novel technique estimating BRS based on the closed-loop assumption, a new method was proposed that the sequence method is applied to a time series generated by the identified multivariate autoregressive (MAR) model driven by the innovation process, tentatively called "innovation method". Comparison between the estimates obtained by the sequence and the innovation methods did not s … More how large disparity, which clears the difference in the absolute value of BRS estimated by the open- and closed-loop techniques. In addition, the closed-loop impulse response from BP to BP was found to be accelerated as the orthostatic stress became heavier. Similar analyses were applied to the data of spinal injury patients. As a result, the cardiovascular system showed unstable responses for the patients of upper level injury. In contrast, the patients of lower level injury were found to have similar characteristics to the healthy subjects. Besides, the patients showed the distinct 0.05Hz oscillation, which could provide novel information concerning generation mechanism of Mayer wave. From the analysis of inter-dependency between BP and HR, the cardiovascular system is considered to be unstabilized by the disconnection between them due to the injury. Because the response to the orthostatic stress reflects control of peripheral resistance and behavior of venous return, the control criteria of the cardiovascular system could be explored by modeling them. Additionally, we constructed the cardiovascular model which consists of HR and sympathetic activity as control variables and BP as a variable to be controlled. Simulation of optimal control on the model suggests that the criteria for generating 1/f fluctuation in HR are loose ones allowing deviations to some extent rather than rigid one not allowing fluctuations. Less