Chaos analysis of blood pressure and heart rate variability in hypertension

为了研究高血压患者动脉压和心率变异性（HRV）的非线性和线性成分，我们构建了时间序列数据的混沌和频谱分析系统，并将其应用于临床。在计算机中取无创连续血压监测仪或动态心电图的R-R间期数据，进行混沌分析和频谱分析。应用该系统得到了以下结果：(1)对原发性高血压患者（EHT）和正常对照组（NT）的HRV进行混沌和频谱分析，探讨平视倾斜时交感神经活动的系列变化。静止时EHT的%HF降低，两组的俯仰升高了LF/HF，降低了%HF。另一方面，在静止状态下，EHT组的相关维数（复杂性指数）比NT组低，且EHT组在平视倾斜时没有变化，但NT组有所下降。Lyapunov指数（对初始条件的敏感依赖指数）在平视倾斜过程中没有变化。(2)对门诊HT和NT患者的混沌和频谱成分的昼夜变化进行了研究，发现HF %没有昼夜变化，但在NT患者的白天有所下降，LF/HF的变化与HF %相反。另一方面，NT和成人HT的相关维度在白天或晚上都有所下降，但在老年HT中没有变化。夜间老年HT组的Lyapunov指数明显小于老年NT组。综上所述，HRV中包含的混沌分量似乎反映了HRV与光谱分量不同的方面。

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.