非稳定周期轨道在立位心率变异分析中的应用

目的 研究立位心脏R－R间期信号的非稳定周期轨道的结构，进一步探讨心率变异（HRV）的动力学特征。方法 记录8名受试者平卧位5min和立位20min过程中的心电图，检测HRV信号的非稳定周期轨道。结果 立位时高周期数（周期2和周期3）的非稳定周期轨道出现率降低，HRV吸引子变得相对简单；非稳定周期1轨道位置随着体位和时间的改变而改变1。说明HRV的动力学特征有改变，心血管系统的调节功能有改变。结论：非稳定周期轨道可以刻划HRV的动力学性质，是分析HRV的潜在的方法。

The application of unstable periodic orbits in heart rate variability analysis during orthostatic standing

Objective To study structure of the unstable periodic orbits (UPOs) of R-R interval signals of heart during orthostatic standing, and to reveal the dynamic characters of heart rate variability (HRV). Method ECGs of 8 subjects in supine (5 min) and orthostatic standing posture (20 min) were recorded. Unstable periodic orbits of HRV signals were detected. Results As compared with that of supine posture, the occurrence rate of unstable period 2 and unstable period 3 significantly decreased during orthostatic standing, and the chaotic attract of HRV became simpler. The situation of unstable period 1 orbit changed along with the body posture and time continued. It showed that there were changes in the dynamics of HRV and the modulations of cardiovascular system. Conclusion UPOs can be used to characterize the dynamics of HRV and is a potential method to analyze HRV.