Chaos analysis of blood pressure and heart rate variability in hypertension

为了研究原发性高血压患者血压和心率变异性（HRV）的非线性和线性成分，构建了时间序列数据的混沌谱分析系统，并将其应用于临床。将无创连续血压监测仪或霍尔特心电图的R-R间期数据输入计算机后，分别进行混沌分析和频谱分析。通过使用该系统获得了以下结果。(1)本文对原发性高血压患者（EHT）和正常血压对照者（NT）的心率变异性（HRV）进行了混沌和频谱分析，以探讨头高位倾斜时交感神经活动的系列变化。EHT组静息时%HF降低，头高位倾斜增加LF/HF，降低%HF。另一方面，关联维数，一个指数的复杂性，是在休息时EHT低于NT，并没有改变EHT在响应头向上倾斜，但在NT下降。李雅普诺夫指数，对初始条件的敏感依赖性的指标，并没有改变在两组的头向上倾斜。(2)对门诊HT和NT的混沌和光谱成分的昼夜变化进行了研究。HT组的%HF无昼夜变化，而NT组的%HF在白天下降。LF/HF显示与%HF相反的变化。另一方面，在白天或晚上，NT和成人HT的相关维数降低，但在老年HT没有变化。在夜间，老年HT组的Lyapunov指数显著小于老年NT组。总之，心率变异性中包含的混沌成分反映了心率变异性与频谱成分的不同方面。

To investigate nonlinear and linear components of arterial pressure and heart rate variability (HRV) in essential hypertension, we constructed the chaos and spectral analysis system of the time series data, and applied it on clinical settings. After taking the R-R interval data of non-invasive continuous blood pressure monitor or Holter ECG in the computer, both the chaos and spectral analyses were performed. The following results were obtained by using this system.(1) Chaos and spectral analyses of HRV were performed in essential hypertensive subjects (EHT) and normotensive controls (NT) to investigate the serial changes of sympathetic nerve activity during head-up tilting. The %HF was decreased in EHT at rest, and head-up tilting increased the LF/HF and reduced the %HF in both groups. On the other hand, the correlation dimension, an index of complexity, was lower at rest in EHT than in NT, and did not change in EHT in response to head-up tilting, but decreased in NT. Lyapunov exponents, an index of sensitive dependence on initial condition, did not change during head-up tilting in both groups.(2) Circadian changes of chaos and spectral components were investigated in outpatient HT and NT. The %HF did not show circadian changes in HT, but it decreased during the daytime in NT. The LF/HF showed an opposite change to the %HF. On the other hand, the correlation dimension decreased in the daytime or in the evening in both NT and adult HT, but did not change in elderly HT. The Lyapunov exponents were significantly smaller in the elderly HT than in elderly NT during nighttime.In conclusion, the chaos components included in the HRV seems to reflect the different aspect of HRV from spectral components.