Parameters describing the pulse wave

Pulse wave analysis permits non-invasive assessment of arterial elasticity indices. The contour varies in different parts of the circulation. It depends on physiological or pathophysiological conditions of the organism. The pathological events like arteriosclerosis or diabetes have a primary effect to the artery elasticity. Hypertension or some heart diseases also influence the pulse wave velocity and resulted in earlier wave reflections. There are several methods of pulse wave measurements based on different principles and depending on the type of measured pulse wave. The evaluation parameters can be assessed from the time domain, derivations, velocity or frequency domain. The main aim of this review article is to offer a recent overview of pulse wave measurement parameters and main results obtained. The principles of pulse wave measurement and current experience in clinical practice are shortly discussed too.     

Digital Photoplethysmography for Assessment of Arterial Stiffness: Repeatability and Comparison with Applanation Tonometry

Introduction

Arterial stiffness is an independent risk factor for cardiovascular morbidity and can be assessed by applanation tonometry by measuring pulse wave velocity (PWV) and augmentation index (AIX) by pressure pulse wave analysis (PWA). As an inexpensive and operator independent alternative, photoelectric plethysmography (PPG) has been introduced with analysis of the digital volume pulse wave (DPA) and its second derivatives of wave reflections.

Objective

The objective was to investigate the repeatability of arterial stiffness parameters measured by digital pulse wave analysis (DPA) and the associations to applanation tonometry parameters.

Methods and Results

112 pregnant and non-pregnant individuals of different ages and genders were examined with SphygmoCor arterial wall tonometry and Meridian DPA finger photoplethysmography. Coefficients of repeatability, Bland-Altman plots, intraclass correlation coefficients and correlations to heart rate (HR) and body height were calculated for DPA variables, and the DPA variables were compared to tonometry variables left ventricular ejection time (LVET), PWV and AIX. No DPA variable showed any systematic measurement error or excellent repeatability, but dicrotic index (DI), dicrotic dilatation index (DDI), cardiac ejection elasticity index (EEI), aging index (AI) and second derivatives of the crude pulse wave curve, b/a and e/a, showed good repeatability. Overall, the correlations to AIX were better than to PWV, with correlations coefficients >0.70 for EEI, AI and b/a. Considering the level of repeatability and the correlations to tonometry, the overall best DPA parameters were EEI, AI and b/a. The two pansystolic time parameters, ejection time compensated (ETc) by DPA and LVET by tonometry, showed a significant but weak correlation.

Conclusion

For estimation of the LV function, ETc, EEI and b/a are suitable, for large artery stiffness EEI, and for small arteries DI and DDI. The only global parameter, AI, showed a high repeatability and the overall best correlations with AIX and PWV.     

In vivo repeatability of the pulse wave inverse problem in human carotid arteries

Accurate arterial stiffness measurement would improve diagnosis and monitoring for many diseases. Atherosclerotic plaques and aneurysms are expected to involve focal changes in vessel wall properties; therefore, a method to image the stiffness variation would be a valuable clinical tool. The pulse wave inverse problem (PWIP) fits unknown parameters from a computational model of arterial pulse wave propagation to ultrasound-based measurements of vessel wall displacements by minimizing the difference between the model and measured displacements. The PWIP has been validated in phantoms, and this study presents the first in vivo demonstration. The common carotid arteries of five healthy volunteers were imaged five times in a single session with repositioning of the probe and subject between each scan. The 1D finite difference computational model used in the PWIP spanned from the start of the transducer to the carotid bifurcation, where a resistance outlet boundary condition was applied to approximately model the downstream reflection of the pulse wave. Unknown parameters that were estimated by the PWIP included a 10-segment linear piecewise compliance distribution and 16 discrete cosine transformation coefficients for each of the inlet boundary conditions. Input data was selected to include pulse waves resulting from the primary pulse and dicrotic notch. The recovered compliance maps indicate that the compliance increases close to the bifurcation, and the variability of the average pulse wave velocity estimated through the PWIP is on the order of 11%, which is similar to that of the conventional processing technique which tracks the wavefront arrival time (13%).     

高血压患者脉搏波参数与脉搏波传导速度的相关性研究

目的:探讨高血压患者脉搏波参数与脉搏波传导速度的相关性,为从脉图上辨识高血压病及脉搏波参数的拓展应用提供参考。方法:选择2012年6月至2013年6月在北京安贞医院和北京人民医院门诊和住院确诊的原发性高血压患者32例作为实验组,并招募健康成人志愿者29例作为对照组。利用中医四诊合参辅助诊疗仪与皮尺分别采集两组受试者的左侧寸口脉图信息和主动脉至桡动脉的血管长度,计算脉搏波参数及脉搏波传导速度,采用方差分析和皮尔逊简单相关的统计方法分析高血压患者不同的脉搏波参数与其脉搏波传导速度的相关性。结果:与对照组比较,实验组的PWV显著升高,有显著性差异(P0.05)。实验组H2/H1明显高于对照组(P0.05),但H4/H1、T1/T、T2/T比值均显著低于对照组(P0.05),差异均有显著性意义(P0.05)。高血压患者的H2/H1、T1/T、T2/T、H4/H1均与其PWV相关,其中H2/H1与PWV呈显著正相关(P0.05),T1/T、T2/T与PWV呈显著负相关(P0.05),H4/H1与PWV呈一般正相关(P0.05)。结论:高血压患者的脉搏波参数与脉搏波传导速度具有显著相关性,且潮波出现的幅值与脉搏波传导速度有显著正相关;脉搏波上升支和潮波的时值与脉搏波传导速度具有显著负相关,重搏波相对高度与脉搏波传导速度具有一般相关关系,因而可通过脉搏波参数的变化了解高血压患者血管弹性的状态。     

Pulmonary vascular impedance and wave reflections in the hypoxic calf.

The alterations in pulsatile hemodynamics that occur during hypoxic pulmonary vasoconstriction have not been well characterized. Changes in oscillatory hemodynamics, however, may affect right ventricular-pulmonary vascular coupling and the dissipation of energy within the lung vasculature. To better define hypoxic pulsatile hemodynamics, we measured main pulmonary artery proximal and distal micromanometric pressures and ultrasonic flow in four open-chest calves during progressive hypoxia. Main pulmonary artery impedance and pressure transmission spectra were calculated using spectral analysis methods. Measured pressure and flow signals were separated in the time domain into forward and backward components. Hypoxia increased pulmonary blood pressure and resistance and produced multiple modifications in the impedance and pressure transmission spectra that indicated increased wave reflections and elasticity. The impedance and apparent phase velocity first-harmonic values were increased in amplitude, and the pressure transmission modulus plot showed an increased peak value. In addition, the impedance modulus plot demonstrated a rightward shift and increased oscillation in the mid- to high-frequency range. The time domain analysis also confirmed increased wave reflections and elasticity. Hypoxia produced large backward-traveling (reflected) pressure and flow waves. The initial portions of these waves arrived at the heart during systole, producing characteristic changes in the measured pressure and flow waveforms. With prolonged hypoxia, main pulmonary artery pulse wave velocity increased by 30%. Thus, hypoxia is associated with complex alterations in pulmonary artery elasticity and wave reflections that act to increase the oscillatory afterload of the right ventricle.     

Oscillatory structure of the parameters of the pulse signal of the radial artery

The typology analysis of the spectral density curves of time series obtained from various parameters of unit pulse oscillations was performed. The formal classification (typology) of spectral curves was performed using correlations of peak values of the spectral density of VLF, LF, and HF slow waves. To include a spectral density curve into a particular type, the criteria were introduced that characterize the intensity of these oscillatory components. The experimental data was collected during examinations of children and adolescents that were performed to detect the early stage of arterial hypertension (AH). The distribution of the subjects among the types of spectral density based on various parameters of pulse oscillation was evaluated. The results of the comparative analysis of spectral type distribution for various parameters are shown. This analysis has revealed the most informative spectral parameters for differential diagnosis of conditions of two types: type 1, essential hypertension, and type 2, various functional disorders with a normal blood pressure. It has been found that the parameters of the oscillatory components of dicrotic pulse wave time characteristics are the most informative for detecting hypertension in children.     

年轻健康正常人单次精准功率运动前后脉搏波波形特征个体化分析研究*

目的: 观察研究年轻健康正常人的静息桡动脉脉搏波特征及单次个体化运动后脉搏波的变化情况。方法: 选取阜外医院年轻健康、无任何疾病诊断的正常人16例,首先完成症状限制性极限心肺运动试验（CPET）,根据CPET计算Δ50%功率为个体化精准运动强度,完成持续30 min的单次运动。于运动前和运动后10 min、20 min、30 min分别测量50 s桡动脉脉搏波,先用软件自动定点再人工复检得到每个脉搏波特征点：起始点（B）、主波波峰点（P1）、重搏波波谷点（PL）、重搏波波峰点（P2）、结束点（E）,从仪器中导出各点对应的横坐标（时间T）和纵坐标（幅值Y）的原始数据,将上一个脉搏波的结束点E视为下一个波的起始点B,TB归零,得到主要观察指标：YB、YP1、YPL、YP2及TP1、TPL、TP2、TE,并计算出ΔYP1（YP1-YB）、ΔYPL（YPL-YB）、ΔYP2（YP2-YB）,TE-TPL、（TE-TPL）/TPL、脉率,S1（主波升支斜率）、S2（重搏波升支斜率）,ΔYP2-ΔYPL、TP2-TPL作为次要观察指标;定义波峰明显的重搏波为YP2>YPL,计算波峰明显的重搏波出现率（50 s内YP2>YPL的波形个数/波形总个数×100%）;对每位患者运动前后的50 s脉搏波数据个体化分析,再将所有数据求均值进行整体分析。结果: ①16例年轻健康受试者（男10女6）,年龄（30.6±6.4,24~48）岁;身高（170.4±8.2, 160~188）cm;体质量（63.9±12.8, 43~87）kg。②静息时YB（87.2±5.8,78.1~95.9）、YP1（223.5±15.8,192.7~242.3）、YPL（122.8±7.8,110.0~133.8）、YP2（131.4±4.9,116.7~137.5）、TP1（126.2±42.2,94.2~280.0）、TPL（360.2±44.8,311.5~507.3）、TP2（432.4±50.8,376.2~589.0）、TE（899.7±86.9,728.3~1042.0）;ΔYP1（136.3±19.9,96.8~158.6）、ΔYPL（35.7±10.7,16.0~55.7）、ΔYP2（44.3±8.1,22.5~56.5）、TE-TPL（539.5±79.3,405.9~691.3）、（TE-TPL）/TPL（1.5±0.3,0.8~2.0）、脉率（67.3±6.6,57.6~82.4）、S1（1.1±0.2,0.6~1.4）、S2（0.1±0.1,0.0~0.2）、ΔYP2-ΔYPL（8.6±6.1,0.9 ~19.8）、TP2-TPL（72.3±19.9,38.3~108.4）。③运动后10 min, YPL（97.0±13.2比122.8±7.8）、YP2（109.6±12.8比131.4±4.9）、ΔYPL（6.6±9.8比35.7±10.7）、ΔYP2（19.3±11.2比44.3±8.1）显著减小,TE（667.8±123.1比899.7±86.9）、TE-TPL（330.2±128.4比539.5±79.3）、（TE-TPL）/TPL（1.0±0.4比1.5±0.3）显著减小,而脉率（92.2±14.0比67.3±6.6）、ΔYP2-ΔYPL（12.7±9.7比8.6±6.1）、 TP2-TPL（98.0±38.1比72.3±19.9）显著增大（P均<0.05）。运动后20 min和30 min的脉搏波变化趋势与运动后10 min保持一致,但从20 min开始大部分指标逐渐向运动前静息水平恢复。④静息时16例正常人波峰明显的重搏波出现率为94.5%,运动后10 min（96.3%）、20 min（98.5%）、30 min（99.8%）的出现率升高（P均<0.01）。其中10例运动前后波峰明显的重搏波出现率均维持在100%左右;2例运动前出现率已达100%,但运动后10 min有所降低,后又继续升高,30 min时恢复到100%;3例静息出现率偏低,运动后升高近100%;还有1例仅运动后20 min出现率偏低,考虑人为因素影响。结论: 运动对正常人脉搏波的影响主要体现在重搏波上;整体上看,单次精准功率运动后,重搏波位置降低、幅度加深,波峰明显的重搏波出现率普遍提高,且这种改变至少能维持30 min;从个体上看,每位受试者的反应又有所不同。     

One-dimensional model for propagation of a pressure wave in a model of the human arterial network: comparison of theoretical and experimental results

Pulse wave evaluation is an effective method for arteriosclerosis screening. In a previous study, we verified that pulse waveforms change markedly due to arterial stiffness. However, a pulse wave consists of two components, the incident wave and multireflected waves. Clarification of the complicated propagation of these waves is necessary to gain an understanding of the nature of pulse waves in vivo. In this study, we built a one-dimensional theoretical model of a pressure wave propagating in a flexible tube. To evaluate the applicability of the model, we compared theoretical estimations with measured data obtained from basic tube models and a simple arterial model. We constructed different viscoelastic tube set-ups: two straight tubes; one tube connected to two tubes of different elasticity; a single bifurcation tube; and a simple arterial network with four bifurcations. Soft polyurethane tubes were used and the configuration was based on a realistic human arterial network. The tensile modulus of the material was similar to the elasticity of arteries. A pulsatile flow with ejection time 0.3 s was applied using a controlled pump. Inner pressure waves and flow velocity were then measured using a pressure sensor and an ultrasonic diagnostic system. We formulated a 1D model derived from the Navier-Stokes equations and a continuity equation to characterize pressure propagation in flexible tubes. The theoretical model includes nonlinearity and attenuation terms due to the tube wall, and flow viscosity derived from a steady Hagen-Poiseuille profile. Under the same configuration as for experiments, the governing equations were computed using the MacCormack scheme. The theoretical pressure waves for each case showed a good fit to the experimental waves. The square sum of residuals (difference between theoretical and experimental wave-forms) for each case was <10.0%. A possible explanation for the increase in the square sum of residuals is the approximation error for flow viscosity. However, the comparatively small values prove the validity of the approach and indicate the usefulness of the model for understanding pressure propagation in the human arterial network.     

长期慢病患者单次精准功率运动前后脉搏波波形特征个体化分析研究*

目的: 观察研究长期慢病患者的静息桡动脉脉搏波及单次个体化运动后脉搏波的变化情况。方法: 选取被明确诊断为高血压和（或）糖尿病和（或）高脂血症的长期（病程≥5年）慢病患者16例,完成症状限制性极限心肺运动试验（CPET）,计算Δ50%功率为个体化精准运动强度,完成持续30 min的单次个体化运动。于运动前和运动后10 min、20 min、30 min分别测量50 s桡动脉脉搏波,得到每个脉搏波特征点：起始点（B）、主波波峰点（P1）、重搏波波谷点（PL）、重搏波波峰点（P2）、结束点（E）,从仪器中导出各点对应的横坐标（时间T）和纵坐标（幅值Y）的原始数据,将上一个脉搏波的结束点E视为下一个波的起始点B,TB归零,得到主要观察指标：YB、YP1、YPL、YP2及TP1、TPL、TP2、TE,并计算出ΔYP1、ΔYPL、ΔYP2,TE-TPL、（TE-TPL）/TPL、脉率,S1、S2,ΔYP2-ΔYPL、TP2-TPL作为次要观察指标;计算波峰明显的重搏波出现率;对每位患者运动前后的50 s脉搏波数据个体化分析,再将所有数据求均值进行整体分析。结果: ①16例长期慢病患者(男14女2）,年龄（53.7±12.6,28~80）岁,身高（171.7±6.6, 155~183）cm,体质量（80.0±13.5, 54~98）kg。2静息时YB（91.5±10.8,71.1~108.6）、YP1（203.6±24.7,162.7~236.3）、YPL（127.1±6.2,118.2~140.3）、YP2（125.9±6.2,115.7~137.7）、TP1（137.2±22.3,103.0~197.1）、TPL（368.7±29.5,316.3~434.0）、TP2（422.7±32.8,376.9~494.7）、TE（883.4±95.0,672.2~1003.3）,ΔYP1（112.1±33.8,60.3~157.5）、ΔYPL（35.5±14.2,17.5~66.2）、ΔYP2（34.4±13.3,20.0~62.9）、TE-TPL（514.6±85.4,341.4~621.9）、(TE-TPL)/TPL（1.4±0.2,1.0~1.7）、脉率（68.8±8.4,59.8~89.3）、S1（0.9±0.3,0.4~1.4）、S2（0.0±0.0,-0.1~0.0）、ΔYP2-ΔYPL（-1.2±2.6, -6.5 ~2.5）、TP2-TPL（54.0±10.8,33.6~81.1）。③运动后10 min,YB、 YPL、YP2、TPL、TE减小,YP1增大;ΔYPL、TE-TPL、（TE-TPL）/TPL减小,而ΔYP1、脉率、S1、ΔYP2-ΔYPL、 TP2-TPL增大（P均<0.05）。运动后20 min和30 min的脉搏波变化趋势与运动后10 min保持一致,但从10 min后大部分指标逐渐向静息水平恢复。④静息时16例长期慢病患者波峰明显的重搏波出现率为28.6%,运动后10 min（65.7%）、20 min（77.1%）、30 min（73.7%）的出现率明显提高（P均<0.01）。其中6例患者运动后波峰明显的重搏波出现率显著升高,且能持续到30 min;3例患者运动后10 min出现率上升明显,20 min时开始下降;1例患者运动后20 min出现率才开始升高;2例患者运动后10 min出现率升高后随即下降;1例患者运动后20 min出现率短暂升高后下降;1例患者运动后出现率下降,20 min时开始回升;2例患者运动后出现率不升,30 min时稍有升高。结论: 长期慢病患者的桡动脉脉搏波波形矮小,重搏波不明显甚至消失,单次精准功率运动后,主波增高,重搏波位置降低、幅度增大;具体反应情况应个体化分析。     

Evaluation of blood flow velocity waveform in common carotid artery using multi-branched arterial segment model of human arteries

Arteriosclerosis is considered to be a major cause of cardiovascular diseases, which account for approximately 30% of the causes of death in the world. We have recently demonstrated a strong correlation between arteriosclerosis (arterial elasticity) and two characteristics: maximum systolic velocity (S1) and systolic second peak velocity (S2) of the common carotid artery flow velocity waveform (CCFVW). The CCFVW can be measured by using a small portable measuring device. However, there is currently no theoretical evidence supporting the causes of the relation between CCFVW and arterial elasticity, or the origin of the CCFVW characteristics. In this study, the arterial blood flow was simulated using a one-dimensional systemic arterial segments model of human artery in order to conduct a qualitative evaluation of the relationship between arterial elasticity and the characteristics of CCFVW. The simulation was carried out based on the discretized segments with the physical properties of a viscoelastic tube (the cross-sectional area at the proximal and terminal ends, the length, and the compliance per unit area of the tube (C_S)). The findings obtained through this study revealed that the simulated CCFVW had shape similar characteristics to that of the measured CCFVW. Moreover, when the compliance C_S of the model was decreased, the first peak of the simulated-CCFVW decreased and the second peak increased. Further, by separating the anterograde pulse wave and the reflected pulse wave, which form the CCFVW, we found that the decrease in the first peak of the simulated CCFVW was due to the arrival of a reflected pulse wave from the head after the common carotid artery toward the arrival of a anterograde pulse wave ejected directly from the heart and that the increase in the second peak resulted from the arrival of the peak of the reflected pulse wave from the thoracic aorta. These results establish that the CCFVW characteristics contribute to the assessment of arterial elasticity.     

Pressure and flow in the systemic arterial system

The dynamic characteristics of the proximal arterial system are studied by solving the nonlinear momentum and mass conservation equations for pressure and flow. The equations are solved for a model systemic arterial system that includes the aorta, common iliacs, and the internal and external iliac arteries. The model includes geometric and elastic taper of the aorta, nonlinearly elastic arteries, side flows, and a complex distal impedance. The model pressure wave shape, inlet and outlet impedance, wave travel, and apparent wave velocity compare favorably with the values measured on humans. Calculations indicate that: (i) reflections are the major factor determining the shape and distal amplification of the pressure wave in the arterial tree; (ii) although important in attenuating the proximal transmission of reflecting waves, geometric taper is not the major cause of the distal pressure wave amplification; (iii) the dicrotic wave is a result of peripheral reflection and is not due to the sudden change in flow at the end of systole; (iv) the elastic taper and nonlinearity of the wall elasticity are of minor significance in determining the flow and pressure profiles; and (v) in spite of numerous nonlinearities, the system behaves in a somewhat linear fashion for the lower frequency components.     

Simulations of arterial pressure pulses using a transmission line model

Transmission of pressure pulses from the aorta to the central retinal artery is studied under normal and stenotic conditions. A convenient model for the study is obtained by replacing the arteries with a network of distributed electrical transmission lines. By using boundary conditions and a voltage-pressure analogy, the transmitted pulse is obtained. Stenosis of varying degrees were simulated at different locations and the characteristics of the transmitted pulse was studied by examining its peak value, the dicrotic notch and the systolic slope. The dependence of the characteristics of the transmitted pulse on the physical parameters were also studied.     

Measurements of the elasticity of monolayers consisting of lipids from nerve membranes

For measurement of viscoelastic properties of monolayer-covered interfaces a longitudinal wave is generated in the plane of the interface, using a horizontal oscillating barrier. The wave propagation depends on the values of the viscoelastic parameters of the monolayer. The technique is applied here to study the surface elasticity of layers consisting of lipids extracted from nerve membranes. It is concluded that mechanical disturbances are propagated as longitudinal waves. The possibility that longitudinal waves occur in nerve membranes and the role they might play in the transmission of information in biological membranes is discussed.     

Effect of colchicine on atherosclerosis. I. Clinical and biological studies

The effect of colchicine was studied in 51 hypertensive subjects with several other vascular risk factors. Colchicine was administered for 3-4 months in a daily dose of 1 mg per os. The treatment did not change the lipid content in the blood and in skin biopsies, and had no effect on systolic and diastolic blood pressure. On the contrary, colchicine treatment significantly improved the conjunctival biomicroscopy score, the duration of the dicrotic wave and the peripheral resistance index. The results show the improvement of the microcirculatory parameters (elasticity of arteries) without changes of serum and tissue lipid parameters in the patients treated with colchicine.     

Spectral and Coherent Analysis of the Relationship between Pulse Wave Forms in the Carotid Artery and Heart Rate

The purpose of this study was the assessment of the parameters of pulse waves in the carotid artery and their relationships with baroreflex-controlled heart rate variability. The early systolic peak (ESP) is closely connected with the filling of the carotid artery, whereas the late systolic peak (LSP) shows the amplitude of the wave reflected from the periphery and affects arterial pressure oscillations activating baroreceptors and changing the heart rate (HR). A cardiac rhythmogram and pulse pressure waves in the carotid artery were continuously recorded for 5 min. ESP and LSP amplitudes (in ml/l) were evaluated in each wave. Patients with coronary artery disease and healthy subjects were examined. Spectrum analysis and assessment of the coherent function between RR intervals, the ESP, and the LSP in the middle frequency band were performed. In healthy subjects, the amplitude of the ESP was higher than that of the LSP, whereas, in patients, the LSP amplitude surpassed that of the ESP. The LSP/ESP ratio was significantly higher in patients, indicating that artery dilation depended more on the reflected wave than on the primary wave. The study revealed that age had the most pronounced effect on the LSP/ESP ratio. Healthy subjects showed the highest age-dependent coherence between the RR interval and the ESP amplitude, whereas in patients this coherence was significantly lower. Measurement of the ESP and LSP amplitudes and their ratio allowed evaluation of vasomotor artery tone. Age and disease produced the maximum effects on the artery tone and decreased the correlation between the changes in the artery tone and the HR in the baroreflex range of frequency regulation.     

Model-based cardiovascular disease diagnosis: a preliminary in-silico study

In this study, we developed and examined the feasibility of a model-based system identification approach to cardiovascular disease diagnosis. The basic premise of the approach is that it may be possible to diagnose cardiovascular disease from disease-induced alterations in the arterial mechanical properties manifested in the proximal and distal arterial blood pressure waveforms. It first individualizes the lumped-parameter model of wave propagation and reflection in the artery using the measurement of proximal and distal arterial blood pressure waveforms. Then, it employs a diagnosis logic, in the form of disease-specific patterns in model parameters, referred as \(\alpha , \beta \) and pulse transit time. The longitudinal change in these parameters is used to diagnose the presence of peripheral artery disease and arterial stiffening. We illustrated the feasibility of the proposed approach by testing it in a full-scale in-silico arterial tree simulation. The results showed that the approach exhibited superior sensitivity to ankle-brachial index and convenience to carotid-femoral pulse wave velocity: The model parameters \(\alpha \) and \(\beta \) responded with up to 100 and 40 % changes to peripheral artery disease with up to 50 % arterial blockage whereas the change in ankle-brachial index was \({<}5\,\%\); the same parameters responded with up to 300 and 40 % changes to up to 100 % arterial stiffening while pulse transit time changed by up to 24 %. Together with the development of more convenient techniques for the measurement of arterial blood pressure waveforms, the proposed approach may evolve into a viable alternative to the state-of-the-art techniques for cardiovascular disease diagnosis.     

系统性红斑狼疮患者及吸烟人群颈动脉弹性的对比研究

目的:应用血管回声跟踪技术(E-tracking,ET)的定量评估功能,探讨系统性红斑狼疮及吸烟因素对颈动脉弹性的影响程度。方法:应用血管回声跟踪技术测量44例系统性红斑狼疮患者、56例吸烟人群及30例正常人群颈动脉弹性参数,包括测量血管的压力应变弹性系数(Ep)、硬化参数(β)、顺应性(AC)以及脉搏波传导速度(PWVβ)。测量颈总动脉内中膜厚度(IMT)。组间均数比较采用独立样本t检验,所有数据均以x±s表示,以P0.05为差异具有统计学意义。结果:1.系统性红斑狼疮组Ep、β、PWVβ较正常对照组明显增高,AC较正常对照组明显减低(P0.05);2.吸烟组Ep、β、PWVβ较正常对照组明显增高,AC较正常对照组明显减低(P0.05);3.系统性红斑狼疮组Ep、β、PWVβ较吸烟组明显增高,AC较吸烟组明显减低(P0.05)。结论:系统性红斑狼疮这种全身免疫性疾病较吸烟因素对颈动脉弹性的影响更为显著。     

Protective effects of ascorbic acid on arterial hemodynamics during acute hyperglycemia

Mortality increases when acute coronary syndromes are complicated by stress-induced hyperglycemia. Early pulse wave reflection can augment central aortic systolic blood pressure and increase left ventricular strain. Altered pulse wave reflection may contribute to the increase in cardiac risk during acute hyperglycemia. Chronic ascorbic acid (AA) supplementation has recently been shown to reduce pulse wave reflection in diabetes. We investigated the in vivo effects of acute hyperglycemia, with and without AA pretreatment, on pulse wave reflection and arterial hemodynamics. Healthy male volunteers were studied. Peripheral blood pressure (BP) was measured at the brachial artery, and the SphygmoCor pulse wave analysis system was used to derive central BP, the aortic augmentation index (AIx; measure of systemic arterial stiffness), and the time to pulse wave refection (Tr; measure of aortic distensibility) from noninvasively obtained radial artery pulse pressure (PP) waveforms. Hemodynamics were recorded at baseline and then every 30 min during a 120-min systemic hyperglycemic clamp (14 mmol/l). The subjects, studied on two separate occasions, were randomized in a double-blind, crossover manner to placebo or 2 g intravenous AA before the initiation of hyperglycemia. During hyperglycemia, AIx increased and Tr decreased. Hyperglycemia did not change peripheral PP but did magnify central aortic PP and diminished the normal physiological amplification of PP from the aorta to the periphery. Pulse wave reflection, as assessed from peripheral pulse wave analysis, is enhanced during acute hyperglycemia. Pretreatment with AA prevented the hyperglycemia-induced hemodynamic changes. By protecting hemodynamics during acute hyperglycemia, AA may have therapeutic use.     

Resonance oscillations in the human arterial system]

The paper summarizes the results of the experiments aimed at obtaining sphygmograms of peripheral and carotid arteries with due regard to the values of longitudinal dimensions of body and extremities in healthy subjects. Mathematical equations expressing the fact that dicrotic waves recorded on sphygmograms are the reflections of blood eigentones coinciding with resonance oscillations have been derived. It is proved that at least two partial vibration systems oscillating with different own frequencies are present in human arteries. Conditions under which the resonance of constituent frequencies of pulsatile pressure waves and output waves in arteries occurs have been determined. From this point of view a new explanation for the well-known phenomenon of the pulsatile wave amplitude increase from the heart towards peripheric regions is proposed.     

Arterial pulse wave velocity measurement: different techniques, similar results—implications for medical devices

Different characteristic points used for the evaluation of pulse wave velocity (PWV) give significantly different results. Hence, the accuracy of using these points is questionable. There is need for quantitative comparison of different techniques to determine PWV. Previous studies aimed at comparing different PWV measurement techniques have been noted, however, on a limited number of smaller animals (mice, dogs, etc.). This simulation-based study aims to compare different techniques for PWV measurement in a large representative human population. A computer model is developed for simulating the pressure wave propagation between the carotid and femoral arteries. Using relationships observed in clinical trials, the model input parameters for a statistically representative population are expressed in terms of a person’s age, gender and height. The model is used to calculate the carotid–femoral pressure ratio for different individuals, which is then parameterised into a number of features, and the equivalent propagation time is calculated using the phase-slope method. Using this time, the apparent phase velocity is determined and compared with PWV determined by the foot-to-foot technique. The two velocities compare well with a difference of 0.0059±0.0904 m/s. An averaging criterion for the calculation of apparent phase velocity has been tested and shown to give good estimates compared to the foot-to-foot technique. As it does not involve the identification of characteristic points on the measured pressure waves, the phase-slope method is more suitable for implementation in PWV monitors.