We aimed to assess the effects of acupuncture by analyzing the frequency content of skin blood-flow signals simultaneously recorded at the Hegu acupoint and two nearby nonacupoints following acupuncture stimulation (AS). Laser Doppler flowmetry (LDF) signals were measured in male healthy volunteers in two groups of experiments: needling the Hegu acupoint (n = 13) and needling a nearby nonacupoint (control experiment; n = 10). Each experiment involved recording a 20 min baseline-data sequence and two sets of effects data recorded 0–20 and 50–70 min after stopping AS. Wavelet transform with Morlet mother wavelet was applied to the measured LDF signals. Needling the Hegu acupoint significantly increased the blood flow, significantly decreased the relative energy contribution at 0.02–0.06 Hz and significantly increased the relative energy contribution at 0.4–1.6 Hz at Hegu, but induced no significant changes at the nonacupoints. Also, needling a nearby nonacupoint had no effect in any band at any site. This is the first time that spectral analysis has been used to investigate the microcirculatory blood-flow responses induced by AS, and has revealed possible differences in sympathetic nerve activities between needling the Hegu acupoint and its nearby nonacupoint. One possible weakness of the present design is that different De-Qi feelings following AS could lead to nonblind experimental setup, which may bias the comparison between needling Hegu and its nearby nonacupoint. Our results suggest that the described noninvasive method can be used to evaluate sympathetic control of peripheral vascular activity, which might be useful for studying the therapeutic effects of AS.

We used laser Doppler flowmetry (LDF) and spectrum analysis to investigate the microcirculatory responses to pressure stimulation (PS) of the skin surface. A control group without PS applied, and four groups with different PS (20, 60, 100 and 160 mmHg in groups PS(20), PS(60), PS(100) and PS(160), respectively) were formed from seven volunteers. Each experiment involved recording a 20 min baseline and two effect data recorded at 0-20 and 50-70 min after stopping PS. The relative energy contribution (REC) in five frequency bands revealed by Morlet-wavelet transformation was calculated. At the pressed site, the dc component of the flux signal in the second effect increased significantly only in group PS(60) compared with the control values. The REC was significantly increased in a myogenic-related band in groups PS(60), PS(100) and PS(160), and was significantly decreased in a nerve-related band only in group PS(160). Different PS magnitudes compress vessels to different extents. The proposed vessel-pressing model-which is supported by the results of spectral analysis of flux signals-might help to elucidate the underlying mechanism. The study results indicate that an improved perfusion was sustained for the longest time when applying 60 mmHg PS. This might aid the development of techniques for improving skin microcirculatory perfusion.

It was demonstrated that the application of mild CS significantly changes several harmonic-analysis indexes of the BPW and the PPG waveforms. By providing detailed information about the pulse transmission of each frequency component, harmonic analysis may improve the ability to detect arterial elastic properties induced by CS, other forms of external stimulation, or pathological factors. It may be pertinent to the development of medical devices for application in telemedicine.

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In the present study, laser Doppler measurement was used to quantitatively investigate the microcirculatory effects of contact pressure stimulation (PS) underneath the Hoku acupoint and its nearby nonacupoint, to improve the understanding of the mechanisms underlying acupressure therapy. A control group (no PS applied) and three experimental groups with different applied PS (group A, 60 mmHg on the Hoku acupoint; group B, 60 mmHg on a nearby nonacupoint; group C, 50 mmHg on a nearby nonacupoint) were studied. Each experiment involved recording data of a 20 min baseline and two periods of effects after stopping PS. The relative energy contribution (REC) in five frequency bands, as revealed by Morlet wavelet transformation, was calculated. At the pressed site, the average value of the laser Doppler flux signal was increased only in group A, and coefficient of variance of the amplitude sequence was only significantly decreased during measurement (M1: 0 to 20 min) in group B. The RECs of the myogenic-related band were significantly increased in groups A and C, whereas there were no significant changes found in group B. The improved microcirculatory blood-flow perfusion at Hoku may partly explain why acupressure can exert better therapeutic effects than PS applied to other sites. The laser Doppler spectra responses illustrated that the induced pressure-induced vasodilation can be attributed mainly to the myogenic response. Laser Doppler measurement and analysis therefore represent a noninvasive method of examining the microcirculatory efficacy of acupressure therapy.