Yuh-Ying Lin Wang

Resonance. The missing phenomenon in hemodynamics.

To simulate a short segment of the aorta, we studied wave propagation in an elastic tube with a side branch balloon. The small balloon simulated the organ (group of arterioles). Ligation of this side branch would reduce the moduli of the higher harmonics when the length of the side branch was appropriate. Electrical analogy of vessels was used to analyze this phenomenon. This simulation can explain the ligation results we found in rats. It may also clarify the discrepancies between the prediction of the Womersley equation and the experimental results. We suggest that the aorta and the closely attached organ can produce coupled oscillation; theoretically, this structure is equivalent to a resonance circuit.

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.

Pressure pulse velocity is related to the longitudinal elastic properties of the artery

It is known that arteries in their natural position are always subject to a longitudinal stress. However, the effect of this strong longitudinal tension has seldom been addressed. In this paper, we point out that the traditional pulse wave velocity formulae considering only the circumferential elasticity fail to include all the important energies. We present a vigorous derivation of a pressure wave equation, the pressure wave equation with total energy, which considers all the important energies of the whole arterial system by treating the arterial wall and the blood as one system. Our model proposes that the energy transport in the main arterial system is primarily via the transverse vibration motion of the elastic wall. The final equation indicates that the longitudinal stress is essential and the high frequency phase velocity is related to the longitudinal tension along the arterial wall and its Youngs shearing modulus. By applying this equation, we suggest that longitudinal elastic property is an important factor in hemodynamics and in the treatment of cardiovascular diseases.

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.

Past, Present, and Future of the Pulse Examination (脈診 mài zhěn)

The pulse examination (脈診 mài zhěn) is a unique diagnostic approach of Traditional Chinese Medicine. The description of pulse examination in the history of Traditional Chinese Medicine is full of amazement and mythology. After researching in hemodynamics and investigating in clinical application for three decades, this article describes the development and the merits and demerits of pulse examination. The experiences of the ancients are tried to be illustrated with modern knowledge and language. As the theory of resonant blood circulation is discovered, Traditional Chinese Medicine could be on the shoulder of Newton and then lead the development of modern medicine. Hope the tool of pulse examination constructed according to eigen-vector with specific time domain and position can bring the running water for Traditional Chinese Medicine. Quantitative research could overcome the plight of analog logic qualitative research, and therefore bring new health revolution.

Hemodynamics with total energy

The arterial vessel is considered together with the blood as a whole system. Taking all the potential energies into account, the system is subjected not only to the pressure gradient force but also to the elastic forces arising from the longitudinal stretching and the circumferential stretching. It is the longitudinal stretching force that takes the whole arterial system together, and makes the energy traveling from one Windkessel unit to the adjacent Windkessel unit.

Effects of Captopril on Specific Harmonic Indexes of the Peripheral Pressure Pulse Waveform

There were evidences that the blood pressure measured on the radial artery under some vasodilators treatments will overestimate than which measured on the central artery. Our previous studies infer that the harmonic proportion of the 4th harmonic (C4) of the peripheral pressure pulse waveform could be an index related to the peripheral vascular tone. In this study, we used a vasodilator drug, captopril to verify the relationship between C4 and vasoactive drug. Thirteen male Wistar Kyoto rats weighing 270 to 350 grams were studied. The blood pressure waveforms measured on the tail artery were averaged every 10 minutes and Fourier transformed into frequency domain. The data measured 20 minutes before captopril (0.83mg/1kg) injection was used as control. Four 10 minutes after-drug data sets were compared with the control. The diastolic (DBP) and systolic (SBP) blood pressures decreased rapidly after captopril injection. The mean pulse pressure A0 has the same decreasing trend but less conspicuously. The harmonic proportion of the 4th harmonic decreases at the beginning but then increases dramatically. These results suggest that C4 could be an index related to the peripheral vascular tone. We present a harmonic based pulse waveform analysis method to provide a peripheral pressure waveform index which may be used to estimate the cardiovascular risk.

Age-Related Changes in Specific Harmonic Indices of Pressure Pulse Waveform

The central elastic arteries and the peripheral muscular arteries are different in their responses to aging. Aorta stiffens in much larger extent with age than peripheral arteries do. Peripheral blood pressure indices such as pulse pressure (PP) or augmentation index (AI) were preferred as surrogates in assessing arterial stiffness for clinical convenience. AI and PP both increase progressively with age.

A modified fast laser-Doppler flowmetry to measure the pulsatile microcirculation in rats

A fast laser-Doppler flowmetry (LDF) is modified from a commercial one to measure the pulsatile microcirculation in rats. The time constant (TC) of the integrator in the analogue circuit of the LDF was modified; the frequency response of the modification was simulated by PSPICE to estimate the high 3 dB frequency. The coefficients of variance of 32 2-second ensembles of flux in the calibration standard measured by the commercial LDF and the modified one were less than 2%. The animal tests also clearly demonstrated the pulsatile microcirculation on the renal cortex in the rat.