Wei-Kung Wang

Microcirculatory characteristics of acupuncture points obtained by laser Doppler flowmetry

Acupuncture points (acupoints) form part of the meridian system that constitutes the most fundamental concept in oriental medicine, but their physiological basis has not been clarified. In this study we employed laser Doppler flowmetry (LDF) to extract the microcirculatory characteristics of acupoints and their surrounding tissues, and we interpreted the results from the viewpoint of microcirculatory physiology. Three groups of measurements were performed focusing on the following two important acupoints in oriental medicine in healthy volunteers (n = 13 for group A and n = 9 for groups B and C, respectively): Hoh-Ku (Li4, on the hand) and Ching-Ku (B64, on the foot). The two groups of measurements around Hoh-Ku (Groups A and B) were so designed as to examine the effect of the direction of the nonacupoint away from the acupoint, whereas comparison between the Hoh-Ku and the Ching-Ku measurements was to verify whether the phenomenon was consistent in the upper and the lower extremities. We found that the mean LDF signals were significantly larger at the acupoints than in their surrounding tissues (all p < 0.05), which indicates a larger blood supply into the microvascular beds of acupoints. The results indicate that the physical properties of the vascular structure of acupoints may affect the perfusion resistance, and thereby modulate the microcirculatory perfusion in accordance with tissue needs. This finding facilitates the localization of acupoints, helps in identifying the connection between microcirculatory physiology and responses to acupoint stimulation, and introduces an objective research method for understanding the mechanisms that underlie oriental medicine.

The ventricular-arterial coupling system can be analyzed by the eigenwave modes of the whole arterial system

In response to harmonic forces generated by the heart, the arterial system executes strong coupled distributed oscillatory motions. These oscillations are described by a pressure-area wave equation, which is solvable subject to appropriate Sturm–Liouville boundary conditions. The response pressure can be represented as a sum of stationary waves which are the eigenmodes of the whole arterial system. Natural frequencies of the system are related to the eigenvalues and the phase velocity. Matching of these natural frequencies with heart rate or its harmonics is important in ventricular-arterial coupling. Transfer functions for the pressure can be constructed from the corresponding eigenfunctions.

Organ‐specific ligation‐induced changes in harmonic components of the pulse spectrum and regional vasoconstrictor selectivity in Wistar rats

It has been shown previously that the amplitudes of the harmonic components of the pulse spectrum vary in specific patterns when the arteries leading to different organs are ligated, with the variations in the harmonics being linearly additive. Since ligation can be regarded as a vast increase in organ resistance, the present study examined the potential of using these ligation‐induced variations in the pulse spectrum as reference parameters for an increase in vascular resistance and for regional vasoconstrictor selectivity. A vasoconstrictor, either arginine vasopressin (AVP) or angiotensin II (Ang II), was infused into anaesthetized Wistar rats via the femoral vein for 1 h. The distinct harmonic‐specific drug effects on the pulse spectrum were simulated by combining renal artery and superior mesenteric artery ligations in different ratios, the ratio with the lowest mean square difference determining the regional drug selectivity. The ratios indicated that the effect of AVP on the pulse spectrum was attributable to the combined effect of ligating the renal and superior mesenteric arteries, while the effect of Ang II was attributable to ligation of the renal artery. The results are comparable with those of investigations of regional vascular resistance performed using traditional methods. Our findings indicate that the ligation‐induced variations in the pulse spectrum can be used to determine regional increases in vascular resistance. This implies that blood pressure can be used as the sole parameter to determine which arterial bed has been affected by the vasoconstrictor, and how seriously.

Pulse Analysis as a Possible Real-Time Biomarker Complementary to SGPT and SGOT for Monitoring Acute Hepatotoxicity

Based on the resonance theory, the pressure wave of the arterial system could reflect the physical condition of the internal organs. Experimental evidence indicates that the physical condition of organs is related to various Fourier components of the pressure pulse. We have proved that the first harmonic of the pressure-wave spectrum is closely related to the liver. In this study, Wistar rats given massive doses of acetaminophen were examined. The amplitude of the first harmonic of the blood pressure pulse, A1, was analyzed and correlated with the blood liver function indexes that examine serum glutamate pyruvate transaminase (SGPT) and serum glutamic oxaloacetic transaminase (SGOT). When A1 was below 3650 and SGPT was above 90, the kappa value was about 0.6; the probability is greater than. 999 based on a chi-square test. When A1 was below 3650 and SGOT was above 380, the kappa value was around 0.5; the probability is greater than. 999. Our results indicate that A1 may be used as a simple, real-time biomarker that is complementary to the commonly used first-line liver indicators, SGPT and SGOT levels, for monitoring acute hepatotoxicity. It promises a noninvasive, real-time liver-function monitoring method.

Analysis of transverse wave as a propagation mode for the pressure pulse in large arteries

A general axial momentum equation for fluid inside a transverse vibrating elastic tube is derived here. In a system with high pressure and low elastic modulus, transverse motion of the wall contributes important nonlinear forces, and the longitudinal fluid wave which assumes that flow is governed by the Navier-Stokes equation cannot describe the pulse wave completely. By comparing the transverse elastic wave with the longitudinal fluid wave, we conclude that transverse wave is a significant wave mode in large arteries. The longitudinal stress force, commonly ignored in the literature, can be considered as a significant factor that influences the propagation of the arterial pulse.

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 LDFs main drawback of providing only qualitative measurement.

The Physical Conditions of Different Organs Are Reflected Specifically in the Pressure Pulse Spectrum of the Peripheral Artery

We try to solve the “hemodynamic inverse problem” of the internal organs in terms of the peripheral pressure pulse spectrum analysis. Side-branch organs are approximated as resonators with own natural frequencies. They are depicted not as ordinary reflection sites but as antennas that receive energy from the main artery and undergo forced oscillations with selective frequencies. Every organ also reacts back to the main artery as a secondary “small heart source” that generated harmonic forces with maximum amplitude near its own natural frequency. The whole arterial system is in a steady distributed oscillatory state that is the superposition result of encountering the forces generated by the heart and many internal organs. A “frequency matching” theory of the organ and the main artery is proposed. The Fourier components of the pressure pulse in the arterial system are related to the matching conditions of different organs. In vivo studies in kidney and spleen of rats are provided.

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.

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.

Effects of whole-body mechanical stimulation at double the heart rate on the blood pressure waveform in rats

The effects of mechanical stimulation on hemodynamics, such as due to mechanotransduction in vascular endothelial cells, have been widely discussed recently. We previously proposed a resonance model in which the arterial system is treated as a pressure-transmitting system, and suggested that the application of external mechanical stimulation with frequencies near the heart rate (HR) or harmonics thereof can be sensed by the arterial system and induce hemodynamic changes. In this study, we monitored the effects of external mechanical stimulation at a frequency of double the HR on BPW (blood pressure waveform), HRV (HR variability) and BPHV (blood-pressure-harmonics variability) in rats. A motor beating a waterbed mattress was used to generate pressure variations of 0.5 mmHg to apply onto the rats. The experiments were performed on three groups of rats with different beating frequencies: (A) double the HR, (B) 5% deviation from double the HR and (C) 1.5 times the HR. The experimental procedure was a 15 min control period followed by application of the mechanical stimulation for 15 min and further recording for 15 min (OFF period). During the OFF period, the amplitude of the second harmonic in the BPW significantly increased by >5% in group A with decreased HRV and BPHV. The second harmonic increased less in group B, and decreased in group C. The increase in the second-harmonic amplitude in group A may be due to the filtering properties of the renal arterial structure. This mechanism could be used to improve the local blood supply into the kidneys, and hence provide a new treatment modality for some important diseases, such as renal hypertension or nephrosis.