心动周期信号的混沌特征分析及应用

目的:研究心动周期信号(HPS:Heart period signal)的混沌特征和谱特征,及这些特征随年龄的变化.背景:描述心动周期信号的混沌特征的参数有:相对分散度(Hrd),李雅普诺夫指数(Hle),分维数(Hfd)以及我们提出的混沌度(Lcc: Chaosness of HPS).目前只有分维数与年龄关系的初步工作发表,未见有全面研究HPS的混沌特征的工作报道.方法:将264例14～69岁健康自愿受试者分成6个年龄组(10～19,20～29,30～39,40～49,50～59,60～69),用本室研制的计算机化心动周期信号混沌分析系统进行测试.采用CM5导联,采样频率300Hz,AD转换精度12位,提取512个心动周期,计算Hrd, Hle, Hfd,Lcc以及总功率(Tfp)及三分段的绝对及相对功率(Pvv, Plv, Phv, Pvr, Plr, Phr)及平衡参数Rvh,Rlh(Rvh=Pvv/Tfp, Rlh=Plv/Tfp),给出HPS时域图,相平面图(Phase Plane Plot),延迟映射图(Return map)以及功率谱.结果:1.四个混沌特征参数及功率谱的绝对及相对功率和总功率都随年龄的增加而降低,降低的重要原因是反映迷走活动的HPS的高频分量降低.2.功率谱参数中降低最快的是Phv及Phr.3.得出了以上参数随年龄变化的拟合方程及四个混沌特征参数之间的互相关方程和相干系数.4.平衡参数Rvh随年龄增加而增加;5.Rlh先升后降.讨论:1.HPS混沌特征参数随年龄的增加而降低,反映自主神经系统功能的降低,而且主要是迷走神经系统功能的降低,若能有效地保护迷走神经系统,提高迷走神经系统功能,将是抗衰老的重要措施.2.病理条件下,最易受损害的是迷走神经系统;3.混沌特征参数在预测和估计病情的严重性方面是比功率谱参数(如平衡参数Rvh)更为敏感的指标.     

正常人心动周期信号（HPS）的混沌特征随年龄变化──HPS的功率谱分析

心动周期信号（ＨＰＳ）具有混沌特征，携带有自主神经功能信息。ＨＰＳ的功率谱分析可以定量地评价交感、副交感神经活动的强弱及其相互作用。这种方法是测试自主神经系统功能的现代方法。我们利用自行研制的计算机化心动周期信号混沌分析系统，对２１７例正常人的心动周期信号进行了功率谱分析。本文介绍了研究中采用的功率谱指标（Ｐｖｖ、Ｐｌｖ、Ｐｈｖ、Ｐｖｒ、ＰｌｒＰｈｒ、Ｒｖｈ、Ｒｌｈ、Ｔｆｐ），频率指标（Ｖｆｍ、Ｌｆｍ、Ｈｆｍ、ｆｍ、ｆｏ）和混沌度Ｌｏｃ的意义以及它们与年龄的关系。研究表明，随着年龄的增加，交感活动加强，副交感的活动减弱，心脏的混沌程度逐步降低。５０岁左右，有些指标的变化趋势与其它年龄段明显不同。     

正常儿童心动周期混沌特征变化的研究

本文应用计算机化自主神经系统功能测试系统对１０５例正常健康儿童（０～１１岁）进行了心动周期信号混沌特征分析。结果：除ＨＣＣ外，学龄儿童组的四个混沌特征参数均高于学龄前儿童组，新生儿则低于学龄组和学龄前组；功率谱参数学龄儿童组也高于学龄前儿童组。上述结果表明：儿童自主神经系统的发育，是随着年龄的增加而不断成熟的，其调控功能随年龄的不断增长而日趋完善     

新生儿心动周期信号（HPS）的混沌特征,功率谱分析

研究正常新生儿（０～３天）心动周期信号的混沌特征和谱特征，探讨分娩方式对其混沌特征检测值的影响，分析出生体重与各参数的相互关系，新生儿自主神经系统功能发育尚不如儿童期成熟，其交感成分居优势，内外因素对其协调平衡性的影响较小，其原因是否与新生儿对外界刺激反应迟钝有关还值得进一步研究。     

围产期母亲和胎儿心动周期信号分析

同时分析围产期胎儿和孕妇心动周期信号的数字特征(混沌和谱特征)以评价自主神经系统功能。用可视化程序设计的方法实现提取和分析围产期母亲和胎儿心动周期信号。受试者取仰卧位，心电信号从置于腹壁下部耻骨联合导联获得。胎儿心电信号用小波分解进行信号预处理。采用本实验室已经完成开发的技术实现心动周期信号数字特征的分析。该系统可以评价胎儿和孕妇的自主神经系统功能，特别是分别定量评价交感和副交感神经系统功能；该系统还可用以预测胎儿窘迫。胎儿和其它年龄段的心动周期信号数字特征随年龄的变化提示了自主神经系统的发育、成熟和衰老的生理过程，基于这一点我们可以寻找抗衰老的方法；胎儿的心动周期信号数字特征介于新生儿和成人之间，提示胎儿的自主神经系统的调节可能受母体神经内分泌系统的影响。     

心动周期信号中独立成分的分离

采用一项新的统计信号处理技术——独立成分分析提取心动周期信号子成分。从 10名受试者的仰卧和站立体位分别采集 8m in心电信号 ,进而提取心动周期信号。按时间延迟把心动周期信号分成 5组 ,进行独立成分分析 ,重构出两组成分。两组成分分别经傅立叶变换 ,结果显示一组信号成分集中于低频区域 (称为 IC1) ,另一组集中于高频区域 (称为 IC2 )。从仰卧位到站位 IC1的功率显著增加 (P<0 .0 1) ,IC2的功率没有显著的变化 (P>0 .0 5 ) ,IC1的功率占总功率的比值显著增加 (P<0 .0 1)。两体位的比较研究结果表明采用独立成分分析心动周期信号得到的两组成分中 ,IC1可以表征交感神经系统的活动 ,而 IC2表征了副交感神经系统的活动。由这些成分得到的数字和图谱信息可以分别定量评价交感和副交感神经系统的功能     

麻醉鼠心动周期信号功率谱与体温关系的研究

目的:研究体温变化对麻醉大鼠自主神经系统的影响.方法:健康成年的Wistar大鼠18只,体重250 g～300 g,20%乌拉坦腹腔麻醉,气管插管.用温度计监测肛温.记录类似Ⅱ导联心电,分析心动周期信号功率谱特征.结果:在34℃～39℃体温范围内,心动周期功率谱随体温的升高而降低,心动周期信号(heart period signal,HPS)的超低频带功率谱(APU)随温度升高呈M型走势,高频带(APH)呈W型变化,不同体温下各参数几乎都有显著性变化.结论:大鼠HPS功率谱各项谱参数与体温变化相关,这些谱参数可以反映自主神经系统的调节功能.     

模拟与在体心动周期相似性的评价

用二维超声多谱勒技术对正常人和接受人工主动脉瓣置换者的主动周期进行在体观察的结果表明，心率和收缩比之间、左室收缩时间和射血期之间，分别存在同质的、方向一致和高度密切的直线相关规律；但是在数量关系上则不相同，以左室收缩时间为自变量对射血时间的回归方程中，生理组的左室射血时间显著长于病理组的。以同种主动脉瓣为标准参比瓣所所“确定”的模拟左心循环心动周期中，上述两关系与在体循环规律不仅不同质，而且在数量     

Scaling Characteristics of Heart Rate Time Series Before the Onset of Ventricular Tachycardia

Ventricular tachycardia (VT) provokes sudden cardiac death (SCD), which is a major cause of mortality in developed countries. Implantable cardioverter-defibrillators (ICDs) are an efficient therapy for SCD prevention. In this study we analyze heart rate variability (HRV) in data stored by ICDs. In 29 patients exhibiting VT episodes, the last 1000 normal beat-to-beat intervals are analyzed and compared to an individually acquired control time series (CON). HRV analysis is performed with standard parameters of time and frequency domain as suggested by the HRV Task Force. For scaling analyses of heart rate time series, the fractal dimension is analysed, applying Higuchi’s algorithm (HFD). Furthermore, detrended fluctuation analysis (DFA) is performed. None of the standard HRV parameters shows significant differences between CON and VT. Before the onset of VT, the scaling characteristics by means of HFD and DFA are significantly changed. In conclusion, scaling analysis reveals changes in autonomic heart rate modulation preceding VT.     

Changes in Heart Period, Heart Period Variability, and a Spectral Analysis Estimate of Respiratory Sinus Arrhythmias During Aortic Nerve Stimulation in Rabbits

Changes in heart period, heart period variance (HPV), and the respiratory component of HPV were examined during enhanced negative chronotropic influences on the heart produced by aortic depressor nerve (ADN) stimulation in urethane anesthetized rabbits. Spectral analysis was used to quantify the respiratory component of HPV, respiratory sinus arrhythmia (RSA). The statistic derived from spectral analysis which describes RSA, V?, has been proposed to be sensitive to vagal influences on the heart. Stimulation of the ADN significantly increased V?, heart period, and HPV. However, unlike V? and heart period, HPV values remained elevated following the end of stimulation. Propranolol administration did not alter the magnitude of the evoked increase in V?, heart period, or HPV. In contrast, administration of atropine abolished the increases due to stimulation in all three measures. Heart period exhibited a monotonic relationship with stimulation current intensity. This relationship disappeared after propranolol administration suggesting sympathetic mediation. The results suggest that V? is sensitive to manipulations of vagal influences on the heart. In addition, V? often responds in a different manner from heart period and HPV.     

帕金森病患者加速度信号的嵌入维和关联维特征

帕金森病作为一种运动调节功能障碍性疾病,会显著地降低人体中枢神经系统对肢体的控制能力。本文将G-P算法直接应用于人体行走时产生的加速度信号的混沌动力学研究。通过对帕金森病患者和健康人群加速度信号的动力学特征进行比较后发现,相对于健康人,帕金森病患者加速度信号的嵌入维和关联维均显著减小。结果表明,帕金森疾病会使患者运动神经控制系统的混沌程度减弱,复杂性降低;而且可以通过对有限长一维加速度信号的重构捕捉患者运动神经控制系统动力学特征的改变。本研究的结论对于人体运动神经控制系统的生理建模以及帕金森病的临床诊断具有一定的理论和应用价值。     

Assessment of Chaotic Parameters in Nonstationary Electrocardiograms by Use of Empirical Mode Decomposition

This study addressed the issue of assessing chaotic parameters from nonstationary electrocardiogram (ECG) signals. The empirical mode decomposition (EMD) was proposed as a method to extract intrinsic mode functions (IMFs) from ECG signals. Chaos analysis methods were then applied to the stationary IMFs without violating the underlying assumption of stationarity. Eight ECG data sets representing normal and various abnormal rhythms were obtained from the American Heart Associate Ventricular Arrhythmia database. The chaotic parameters including Lyapunov exponent, entropy, and correlation dimension were computed. The results consistently showed that the 10th IMF (IMF-10) was stationary and preserved sufficient nonlinearity of the ECG signals. Each IMF-10 from the data sets (n = 8) gave a positive dominate Lyapunov exponent (0.29-0.64, p < 0.0001), a positive entropy (0.039-0.061, p < 0.0001), and a noninteger correlation dimension (1.1-1.9). These were evidences of a chaotic dynamic system. We therefore concluded that the original ECG signals must also have chaotic properties. The chaotic parameters did not show significant differences among the eight data sets representing normal sinus rhythm and various abnormalities. This study has demonstrated an effective way to characterize nonlinearities in nonstationary ECG signals by combining the empirical mode decomposition and the chaos analysis methods.     

The Effects of Pharmacological Manipulations that Influence Vagal Control of the Heart on Heart Period, Heart-Period Variability and Respiration in Rats

Changes in heart period (HP), heart-period variance (HPV), and the respiratory component of HPV in freely moving rats were examined following pharmacological manipulations known to influence vagal control of the heart. Spectral analysis was used to quantify the component of HPV associated with respiration which is proposed to be sensitive to vagal influences on the heart. The respiratory component of HPV is described by a statistic, V̌, which is the sum of the spectral densities of the heart period spectrum across the band of frequencies associated with normal respiration. Vagal tone was reflexively enhanced by phenylephrine or peripherally blocked by atropine. Phenylephrine produced biphasic changes in HP and V̌, with the increases lasting from 0.5 to 2 hrs. Atropine resulted in significant decreases in HP, HPV and V̌. These decreases were immediate and sustained throughout the experiment, although there were signiflcant linear increases in HP and HPV from their initial post-injection values. In the saline condition, HP increased linearly across time. Results were discussed in terms of vagal and non-vagal control of the heart. It was suggested that, while all three variables are altered by manipulations of vagal influences on the heart, V̌ seems to be influenced less by non-vagal control than HP and HPV.     

Changes in Heart Period, Heart-Period Variability, and a Spectral Analysis Estimate of Respiratory Sinus Arrhythmia in Response to Pharmacological Manipulations of the Baroreceptor Reflex in Cats

The purpose of the present study was to assess changes in heart period, heart-period variance (HPV), and respiratory sinus arrhythmia (RSA) during manipulations of the baroreceptor reflex in anesthetized cats. Hypertension, induced via phenylephrine infusion, reflexly increases parasym-pathetic activity and decreases sympathetic activity. Hypotension, produced by infusion of nitroprusside, leads to increased sympathetic activity and an inhibition of vagal influences on the heart. Specific autonomic contributions were assessed following administration of practolol, a β-adrenergic blocker, or atropine methyl nitrate. Spectral analysis was used to quantify the component of HPV associated with respiration, i.e., RSA, which is proposed to be sensitive to vagal influences on the heart. The respiratory component of HPV is described by a statistic, V?, which is the sum of the spectral densities of the heart period spectrum across the band of frequencies associated with normal respiration. Hypertension produced an increase in V? which was blocked by atropine infusion, but unaltered by beta-adrenergic blockade. Hypotension decreased V? to near-zero values which persisted after atropine and practolol infusion. These data suggest that V? is determined primarily by vagal factors. Correlations between V? and a previously used criterion measure of vagal tone further support this hypothesis. In contrast, heart period was sensitive to vagal and sympathetic factors. Heart period increases during hypertension were abolished with atropine and heart period decreases due to hypotension were eliminated by beta-adrenergic blockade. These responses are consistent with the notion that heart period is under the control of both sympathetic and vagal factors. Since in an anesthetized preparation RSA is the major source of heart-period variability, HPV responded similarly to V?. The results suggest that the spectral estimate of RSA, V?, is particularly sensitive to blood pressure induced reflexive changes in vagal efferent influences on the heart. It also appears that V? is less influenced by sympathetic factors than heart period, a commonly used estimate of vagal activity.     

中西医结合治疗对肺心病急性发作期血液流变性的影响

慢性肺源性心脏病（肺心病）,由于反复肺部感染,缺氧,易出现弥散性血管内凝血（ＤＩＣ）,从而导致肺血管阻力增加、肺动脉高压,而加重心衰和呼衰。为此我们于１９９２～１９９６年采取中西医结合方法治疗慢性肺心病急性发作期患者６０例,设对照组进行疗效对比,并对二组治疗前后的血液流变性改变及其与疗效的关系进行了分析。１　资料与方法１．１　临床资料肺心病急性发作期患者１０８例,病程２至２４年,均系住院病人。全部患者根据我国第二次肺心病专业会议制定的诊断标准［１］确诊。１０８例患者入院检测血液流变学指标均呈异常…