北京生物医学工程

基于最大Lyapunov指数的心音信号混沌特性分析

Chaotic characteristics of heart sound signals based on the largest Lyapunov exponent

作者：孙丽莎孙丽丽彭响华

单位：                      汕头大学电子工程系(广东汕头 515063)        

关键词：相空间重构；最大Lyapunov指数；S1心音；S2心音；混沌特性

分类号：

出版年·卷·期（页码）：2014·33·1（41-46）

摘要：

目的寻求无创伤的且能自适应信号变化的方法区分正常和异常的心音信号，为临床诊断提供更简捷的参考方法。方法本文以心音信号非线性时间序列最大Lyapunov指数为主线，根据心音信号不同阶段特性的统一性，提出了对信号分阶段进行研究的方法。首先对7种具有代表性的正常和异常心音信号的S1、S2心音分别分3阶段进行相空间重构，然后结合各阶段求得的相空间重构参数计算对应的最大Lyapunov指数，最后对正常、异常心音信号最大Lyapunov指数均值进行比较分析。结果正常S1心音信号的最大Lyapunov指数均值0.1450，远大于异常S1心音信号，正常S2心音信号的最大Lyapunov指数均值也比异常S2心音信号大很多。结论心音信号中确实存在混沌现象，且正常(健康)心脏运动到S1和S2阶段的混沌程度要比异常(病态)时高。

Objective To seek a way non-invasive and adaptive to differentiate the normal and abnormal heart sound signals in order to provide more valuable reference method for clinical diagnosis.Methods This paper made the largest Lyapunov exponent as the mainline.According to the unity of the whole signal in different stages，a method to study the characteristic in stage was proposed.First of all，we made phase space reconstitution for the seven typical normal and abnormal heart sound signals in S1 and S2.Then，we calculated the largest Lyapunov exponents according to the phase space reconstitution parameters.At last，we analyzed the mean values of the largest Lyapunov exponents.Results The mean value of the normal heart sound signals in S1 was 0.145，which was much larger than the abnormal ones，and the mean value of the normal heart sound signals in S2 was also larger than the abnormal ones.Conclusions There are chaotic characteristic in heart sound signals exactly and the degree of chaos in normal heart sound signals is higher than that in abnormal ones.

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