Differences in the skin-surface laser Doppler signals between polycystic ovary syndrome and normal subjects.

BACKGROUND: Women with PCOS may present abnormal hemodynamic alterations and thus may develop vascular damage. This study performed LDF measurements on the skin surface around the leg to verify if beat-to-beat waveform and spectral analysis can help to discriminate the MBF characteristics between PCOS and healthy subjects. METHODS: ECG and LDF signals were obtained noninvasively in PCOS (n = 16) and control (n = 8) subjects. Beat-to-beat waveform and spectral analysis was performed on the LDF signals to obtain the AD, FDT, FRT, and REC of five frequency bands. RESULTS: FRT was significantly larger, AD was significantly smaller, REC of the myogenic-related band was significantly smaller and REC of the heartbeat-related band was significantly larger in the PCOS than in the control subjects. CONCLUSION: This study is the first to reveal that time-domain waveform and spectral analysis performed on skin-surface LDF signals can be used to discriminate the differences in the MBF perfusion condition and the microcirculatory regulatory activities at local vascular beds between PCOS and healthy subjects. These findings may aid the noninvasive early detection of PCOS-induced vascular damage.

Complexity analysis of beat-to-beat skin-surface laser-Doppler signals in diabetic subjects.

MOTIVATIONS: This study performed skin-surface laser-Doppler flowmetry (LDF) measurements with the aim of verifying if complexity analysis applied to the beat-to-beat LDF waveform index can be used to discriminate diabetic, prediabetic, and normoglycemic subjects. METHODS: Sixty-six subjects were assigned to three age-matched groups according to the results of oral glucose tolerance tests. Beat-to-beat analysis was performed on the pulsatile LDF waveform to obtain the pulse-to-mean ratio (AD) and pulse width (PW), and then approximate-entropy (ApEn) values for their 20-minute index sequences were calculated to evaluate the signal complexity. RESULTS: AD and PW did not differ significantly among the three study groups. ApEn values of AD and PW were significantly larger and marginally larger, respectively, in the diabetic group than in the prediabetic and normoglycemic groups. CONCLUSION: These results indicate the presence of significant differences in ApEn indexes among diabetic, prediabetic, and normoglycemic subjects. The presence of increased complexity in the LDF index sequence may be partly attributed to the adaptability of the microcirculatory regulatory activities or the impairment of the homeostasis mechanism of microcirculatory-blood-flow perfusion. The present findings may be pertinent to the early detection of the diabetes-induced impairment of this perfusion.

Complexity analysis of the microcirculatory-blood-flow response following acupuncture stimulation.

Beat-to-beat cardiovascular variability analysis provides important information on the circulatory regulatory activities. Changes in the arterial pulse transmission or the opening condition of arteriolar openings might change the fluctuation pattern of the MBF supply, and thus change the complexity property therein. We performed complexity analysis of beat-to-beat laser Doppler flowmetry (LDF) signals to study the microcirculatory-blood-flow (MBF) response at the needled site (Hegu acupoint) following acupuncture stimulation (AS). LDF signals were measured in male healthy volunteers (n=29). Each experiment involved recording a 20-minute baseline-data sequence and two sets of effects data recorded 0-20 and 50-70min after stopping AS. Approximate-entropy (ApEn) analysis, which quantifies the unpredictability of fluctuations in a time series, was performed on each 20-minute beat-to-beat LDF data sequence. The present findings indicate that AS can not only improve the local blood supply but may also increase ApEn values and decrease MBF variability parameters. This was the first attempt to apply complexity analysis to LDF signals in order to elucidate microcirculatory responses following AS. The observed results are probably attributable to the contradictory effects on the MBF supply induced by AS, which might interfere with the microcirculatory regulatory activities so as to increase the complexity of LDF signals. The present findings could help to identify the mechanism underlying the effects of AS, might aid the development of an index for monitoring the induced microcirculatory regulatory responses, and thus provide an evidence-based connection between AS and modern physiology.

Acupuncture stimulation causes bilaterally different microcirculatory effects in stroke patients.

The aim of this study was to determine the effects of acupuncture stimulation (AS) in stroke patients by analyzing the pulsatile waveform and frequency content of skin blood-flow signals recorded simultaneously on the bilateral skin surface of the head. Laser Doppler flowmetry (LDF) signals were obtained in 18 stroke patients. Each assessment involved a 20-min baseline recording, a 20-min AS, and a further 20-min recording. Significant bilateral differences in LDF parameters were noted following AS, with an increased pulsatile component of the microcirculatory blood flow (MBF), decreased blood-flow resistance, and decreased MBF variability in the vascular beds on the stroke-affected side. Spectral analysis revealed that the vasodilation on the stroke-affected side could be partly attributed to decreased sympathetic neural activity. This is the first study to demonstrate the feasibility of evaluating the cerebral MBF conditions induced by AS in stroke patients by noninvasive LDF measurement. The present skull-intact measurement setup could aid the development of noninvasive detection techniques for determining bilateral differences in the cerebral MBF, and could thus become useful for the efficacy evaluation of treatment techniques for stroke. It might also promote understanding of the mechanisms underlying the responses and possible treatment efficacy of AS as applied to stroke patients.

Assessing the effects of acupuncture by comparing needling the hegu acupoint and needling nearby nonacupoints by spectral analysis of microcirculatory laser Doppler signals.

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.

Effects of acupuncture at the Hoku acupoint on the pulsatile laser Doppler signal at the heartbeat frequency.

We aimed to assess the effects of acupuncture by analyzing the alternating current (AC) component of skin blood-flow signals (around the heartbeat frequency) simultaneously recorded at the Hoku acupoint, which is an important acupoint in oriental medicine, and two nearby non-acupoints following acupuncture stimulation (AS). Laser Doppler flowmetry signals were measured in 28 experiments on nine volunteers. Each experiment involved the recording of a 20-min control-data sequence and two sets of effects data recorded 0-20 min and 50-70 min after the AS had been stopped. The direct current (DC) and AC components (DCflux and ACflux, respectively), pulse width (PW), and foot delay time (FDT) of the flux signal were calculated. The DCflux, ACflux, PW, and FDT were all significantly increased only at Hoku following AS. Regression analysis between the DCflux and ACflux revealed that the slope was largest (>1) at Hoku among the measurement sites. Our results indicated that both the DCflux and ACflux in the microcirculatory perfusion were increased by stimulation at the Hoku acupoint, with the change being greatest for the latter. Parameters calculated from the pulsatile flux waveform, such as the PW and FDT, could contribute to noninvasive evaluations of the sympathetic neural activities and of the improvement in perfusion following AS.

Spectral analysis of the microcirculatory laser Doppler signal at the Hoku acupuncture point.

We aimed to characterize the frequency spectra of skin blood flow signals recorded at Hoku, an important acupuncture point (acupoint) in oriental medicine. Electrocardiogram (ECG) and laser Doppler flowmetry signals were measured simultaneously in 31 trials on seven volunteers aged 21-27 years. A four-level Haar wavelet transform was applied to the measured 20 min laser Doppler flowmetry (LDF) signals, and periodic oscillations with five characteristic frequency peaks were obtained within the following frequency bands: 0.0095-0.021 Hz, 0.021-0.052 Hz, 0.052-0.145 Hz, 0.145-0.6 Hz, and 0.6-1.6 Hz (defined as FR1-FR5), respectively. The relative energy contribution in FR3 was significantly larger at Hoku than at the two non-acupoints. Linear regression analysis revealed that the relative energy contribution in FR3 at Hoku significantly increased with the pulse pressure (R(2) = 0.48; P < 0.01 by F-test). Spectral analysis of the flux signal revealed that one of the major microcirculatory differences between acupoints and non-acupoints was in the different myogenic responses of their vascular beds. This information may aid the development of a method for the non-invasive study of the microcirculatory characteristics of the acupoint.

Microcirculatory effect of different skin contacting pressures around the blood pressure.

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.

Connection between RR-interval length and the pulsatile microcirculatory flow.

The present study used laser Doppler flowmetry (LDF) to investigate the connection between skin microcirculatory flow and the length of the RR interval (LRR). Local heating was performed on healthy volunteers to further elucidate its effect on LDF index. ECG and LDF signals were measured in 102 trials on seven volunteers. Each experiment involved a 5 min control and a 5 min heating-effect sequence. Each laser Doppler flux pulse was categorized into four groups according to its LRR compared with the 5 min average LRR. Synchronized averaging analysis was applied to the four groups of pulses to obtain their averaged waveforms, from which four flux parameters were calculated. The ac component of the flux increased significantly with increasing LRR, and the differences therein between the groups with LRR more than 4% smaller and more than 4% larger than the average LRR increased from 15.8% during the control period to 23.9% during the heating period. Understanding of the different flux responses between the control and local-heating experiments may aid the development of a new index, which helps to avoid LDF's main drawback of providing only qualitative measurement.

Characteristics of harmonic indexes of the arterial blood pressure waveform in polycystic ovary syndrome.

MOTIVATIONS: Patients with polycystic ovary syndrome (PCOS; which is often associated with increased cardiovascular risk factors) may present hemodynamic changes in the cardiovascular system. The aim of the present study was to verify whether harmonic indexes of the arterial blood pressure waveform (BPWs) can be used to discriminate between PCOS patients and healthy individuals. METHODS: Twenty-minute bilateral radial BPW signals were obtained in 20 PCOS patients and 20 healthy individuals. Amplitude proportions (Cn values) and their coefficients of variation (CVn values) were calculated for harmonics 1-10 of the BPW. RESULTS: C1 was significantly larger whereas C4, CV2, and CV6 were significantly smaller in PCOS patients compared with healthy individuals. DISCUSSION: The results of the present study suggest that harmonic-analysis indexes of the BPWs could provide information about the arterial pulse transmission (by monitoring Cn) and cardiovascular regulatory activities (by monitoring CVn). These findings could aid the development of an easy-to-perform, noninvasive, and continuous monitoring technique to improve the detection of PCOS-induced hemodynamic changes.

Effects of acupuncture on the harmonic components of the radial arterial blood-pressure waveform in stroke patients.

MOTIVATION: Stroke induces abnormal microcirculatory blood flow perfusion resistance in cerebral vascular beds, which may in turn alter the arterial pulse transmission. This study aimed to determine if the frequency-domain harmonic index for the blood-pressure waveform is useful in monitoring the microcirculatory blood flow perfusion response in cerebral vascular beds of stroke patients following acupuncture stimulation. METHODS: Bilateral radial arterial blood-pressure waveform and laser-Doppler flowmetry signals were obtained noninvasively before and after acupuncture in 17 stroke patients. The amplitude proportion (Cn) for all the acquired pulses and the coefficient of variance (CVn) for harmonics 1-10 were calculated to evaluate the blood-pressure harmonic variability. RESULTS: The laser-Doppler flowmetry parameters showed that the cerebral microvascular blood flow supply could be improved following acupuncture. For the blood pressure waveform harmonic index, there were significant increases in C5 and C6 and decreases in CV5 and CV7 on the stroke-affected side, but no significant changes on the contralateral side. CONCLUSION: Cn values might reflect changes in arterial pulse transmission, and the blood-pressure-harmonic-variability response might be partly attributable to cardiovascular regulatory activities caused by acupuncture-induced changes in the cerebral microvascular blood flow perfusion. The present findings of blood pressure waveform harmonic analysis may be useful to the development of a noninvasive and real-time technique for evaluating treatment efficacy in stroke patients.

Effects of cold stimulation on the harmonic structure of the blood pressure and photoplethysmography waveforms.

BACKGROUND: Cold stimulation (CS) accompanied by vasoconstriction can increase the stiffness of the arterial system. The vascular responses during CS have been studied using photoplethysmography (PPG), but most have focused on time-domain waveform indexes. Focusing on the radial arterial blood pressure (BPW) and the finger PPG waveforms, we aimed to determine if harmonic index could help to noninvasively characterize the changes in arterial pulse transmission following mild CS. METHODS: Trials were measured on male healthy volunteers (n=29); mild CS was applied by placing a bag filled with 2000 cc of water at a temperature of 19-21°C around the right lower arm. For each experiment, we recorded a 3-min baseline-data sequence, applied local mild CS and recorded a 3-min effect sequence, and then recorded another 3-min effect sequence immediately after stopping CS. BPW and PPG spectra were used to calculate the amplitude proportion (C(n)) and phase angle (P(n)) for each harmonic (for n=1-10) from averages of all the pulses during the measurement period. RESULTS: Several harmonic indexes were prominently increased following CS, including C(4)-C(10) and P(3)-P(10) for the BPW and C(5)-C(10) and P(3) and P(4) for PPG waveforms. CONCLUSIONS: 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.

Acute microcirculatory responses induced by skin-surface vibration stimulation at a frequency near the heart rate.

OBJECTIVE: We aimed to elucidate the frequency-specific microcirculatory blood-flow (MBF) effect induced by weak vibration stimulation (VS) in healthy human subjects. METHODS: VS was implemented by a rod (connected to a DC motor) hitting a water-filled bag. VS was applied to the left palm at frequencies near to the heart rate (HR) (n=35; Group A) and 50% higher than the HR (n=20; Group B), and laser-Doppler-flowmetry measurements were made on the back of the left hand (Site 1). A control group without applying VS was also used (n=21). RESULTS: The mean MBF (MMBF), pulsatile MBF, and pulse width at Site 1 only increased significantly in Group A, and the coefficient of variance of the MMBF sequence increased significantly at Site 1 in Groups A and B. CONCLUSION: These results illustrate the VS-induced changes in the regulatory activities of arteriolar openings, and improvement of the MBF near the VS application site in Group A. The improvement in MBF depended on whether the VS frequency was near to, or higher than the HR. The present findings may be pertinent to amelioration of disease induced by an abnormal MBF.

Relations between beat-to-beat microcirculatory blood flow and variations therein.

OBJECTIVE: Analyzing the beat-to-beat cardiovascular variability (e.g., heart-rate variability analysis) provides important information regarding circulatory autonomic control. The present study aimed to use laser Doppler flowmetry (LDF) and beat-to-beat analysis to elucidate changes in the microcirculatory blood flow (MBF) and variations (MBFV) therein induced by local heating stimulation. METHOD: For each experiment, we applied nonpainful local heating and recorded a 20-min heating effect, which was segmented into four measurements separated by 5 min as M1-M4. DCflux (average LDF flux) was calculated for each pulse, and the coefficient of variance of DCflux (DCCV) was then calculated to evaluate the beat-to-beat MBFV. RESULTS: In the linear regression analysis of the M2-M4 data sequence, the slope between relative changes (compared with M1 values) in DCCV and DCflux, and those between the proceeding DCCV and the subsequent DCflux, were negative (R(2) > 0.40 for all; p < 0.05). CONCLUSION: This is the first study to reveal a possible time-domain relationship between changes in MBF and MBFV parameters. Our results suggest that MBFV evaluated from the beat-to-beat LDF waveform is useful for monitoring the microcirculatory regulatory activities of arteriolar openings, and might therefore be particularly meaningful when evaluating treatment techniques or drugs aimed at improving microcirculatory perfusion.

Differences in the microcirculatory effects of local skin surface contact pressure stimulation between acupoints and nonacupoints: possible relevance to acupressure.

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.

Microcirculatory changes by laser Doppler after infrared heating over acupuncture points--relevance to moxibustion.

BACKGROUNDS: Moxibustion is a commonly used treatment in traditional Chinese medicine (TCM) that involves the application of local heating (LH) at acupoints. OBJECTIVE: We used laser Doppler flowmetry (LDF) and spectrum analysis to investigate differences in the microcirculatory responses to the application of homogeneous LH at Hoku and two nearby nonacupoints. METHODS: Thirty-four trials were performed on 10 male healthy volunteers. For each experiment, we recorded a 20-minute baseline data sequence, then applied LH by an infrared-radiation lamp and recorded another 20-minute heating-effect sequence. The relative energy contributions (RECs) for LDF periodic oscillations in five characteristic frequency regions from 0.0095 to 1.6 Hz (segmented into FR1-FR5) were calculated by wavelet analysis. RESULTS: The flux increased significantly following LH. Decreases in RECs of FR2 and FR3, increases in RECs of FR1 and FR5, and the flux increase following LH were all largest at Hoku. CONCLUSION: Our results suggest that the application of LH to acupoints induces larger therapeutic effects. This might partly account for the physiological mechanism of moxibustion, and could contribute to optimizing the microcirculatory improvement by applying LH treatments. Frequency-band analysis appears to be a promising tool for studying microcirculatory responses induced by various TCM treatments.

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.

Spectral analysis on the microcirculatory laser Doppler signal at the acupuncture point.

We aimed to characterize the frequency spectra of skin blood flow signals simultaneously recorded at Hoku, an important acupoint in oriental medicine, and two nearby nonacupoints to understand the underlying physiological mechanism of acupuncture points. ECG and laser Doppler flowmetry signals were measured simultaneously. A four-level Haar wavelet transform was applied to the measured 20-minute LDF signals, and periodic oscillations with five characteristic frequency peaks were obtained within the following frequency bands: 0.0095-0.021, 0.021-0.052, 0.052-0.145, 0.145-0.6, and 0.6-1.6 Hz (defined as FR1-FR5), respectively. The power in FR3 was significantly larger at Hoku than at the two nonacupoints. Spectral analysis of the flux signal revealed that one of the major microcirculatory differences between acupoints and nonacupoints was in the different myogenic responses of their vascular beds. This information may aid the development of a method to noninvasively study the microcirculatory characteristics of the acupoint.

Study on the microcirculatory blood velocity of acupoint monitored by laser Doppler signal.

Meridian system composed of acupoints is the most fundamental concept to build oriental medicine. In this study, we employ LDF measurement to compare the microcirculatory blood velocity of acupuncture point and its surrounding tissues. Measurements were performed around an important acupoint in oriental medicine, Hoh-Ku (Li4, on the hand), in healthy volunteers. The study presented has shown that the acupoints have significantly slower mean blood velocity than their surrounding tissues (p all < 0.005). This finding facilitates the detection of the position of acupuncture point and helps us to provide a possible connection between microcirculatory physiology and the underlying mechanism of acupoints.