Spectral analysis on the microcirculatory laser Doppler signal of the acupuncture effect

We aim to analyze the frequency content of skin blood flow signals recorded on Hoku following acupuncture stimulation (AS). Each experiment involved recording a 20-minute control-data sequence and two effects data recorded 0-20 and 50-70 minutes after stopping AS, respectively. 4-level Haar-wavelet transform was performed on the measured LDF signals, and periodic oscillations with five characteristic frequency peaks were obtained within the frequency interval: 0.0095-0.021, 0.021-0.052, 0.052-0.145, 0.145-0.6, and 0.6-1.6 Hz, respectively. Band proportion and DC component of the flux signal were calculated to elucidate the effects following AS. At Hoku, the DCflux was significantly increased, the band proportion of the 1st and the 2nd frequency band were significantly decreased, and that of the 5th band was significantly increased following AS. Our results facilitate a non-invasive method to evaluate sympathetic control of peripheral vascular activity between the acupoint and non-acupoints, which may be important for studying the therapeutic effects of AS.