植物神经系统对体位的反应：傅立叶和小波分析
Response of Autonomic Nervous System to Body Positions: Fourier and Wavelet Analysis
摘要：
本文用傅立叶变换和小波变换两种数学方法研究了心血管短期控制系统。时间序列，从心电图和动脉血压持续6分钟，在仰卧位（HD 1），在$90^{\circ}$头低位的第一部分（HD 1），第二部分（HD2）和在恢复期间（REC）进行了分析。使用周期为$T=2^j$（$% j=1$，2，$... $，6）的Haar函数执行小波变换以获得小波系数。功率谱分量在三个频带内分析，VLF（0.003-0.04），LF（0.04-0.15）和HF（0.15-0.4），频率单位周期/间隔。小波变换比傅立叶变换在所有分析周期之间表现出更高的区分度。在傅立叶分析中，R-R间期的LF和收缩压的VLF在不同体位下有明显的差异。对于小波分析，收缩压比R-R间期表现出更明显的差异。这项研究表明，血管和心脏对不同体位的反应存在差异。VLF和LF结果之间的部分分离是这项工作的生理相关发现。
英文摘要：
Two mathematical methods, the Fourier and wavelet transforms, were used to study the short term cardiovascular control system. Time series, picked from electrocardiogram and arterial blood pressure lasting 6 minutes, were analyzed in supine position (SUP), during the first (HD1), and the second parts (HD2) of $90^{\circ}$ head down tilt and during recovery (REC). The wavelet transform was performed using the Haar function of period $T=2^j$ ($% j=1$,2,$... $,6) to obtain wavelet coefficients. Power spectra components were analyzed within three bands, VLF (0.003-0.04), LF (0.04-0.15) and HF (0.15-0.4) with the frequency unit cycle/interval. Wavelet transform demonstrated a higher discrimination among all analyzed periods than the Fourier transform. For the Fourier analysis, the LF of R-R intervals and VLF of systolic blood pressure show more evident difference for different body positions. For the wavelet analysis, the systolic blood pressures show much more evident difference than the R-R intervals. This study suggests a difference in the response of the vessels and the heart to different body positions. The partial dissociation between VLF and LF results is a physiologically relevant finding of this work.
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