脉搏波传播和血管顺应性对体循环和肺循环系统血流特性和心室功率的影响

本文采用耦合模型研究脉搏波传播和血管顺应性对体循环和肺循环血流特性和心室功率的影响。左心室和右心室均采用E-R模型,后负荷系统对于体动脉和肺动脉分别采用T-Y管模型和稍微不对称T管模型,应用脉冲响应法将二者耦合起来。选取生理范围的参数,计算了两个系统的每搏输出量(SV)、每搏输出功(SW)、定常功率(     

前,后负荷对心室功能影响的分析模型

本文建立一种简便的心室分析模型，并以Ｗｅｓｔｅｒｈｏｆ三元件模型表征心室后负荷，同时以心室作功的最小功原理作为心室与血管间匹配耦合的条件，在此基础上，讨论心室前、后负荷对心室压力－容积关系的影响情况，并与Ｓｕｎａｇａｗａ等的实验结果［１］作比较，发现本文所建立的心室、血管和心室－血管耦合模型所得到的表征心室特性的Ｅｅｓ和Ｖｏ与实验结果吻合得相当好，因而本文所建立的分析模型是模拟心室前、后负荷对心室特性的影响和分析心室泵功能的有效模型     

脉搏波的传播和临床脉诊

早在1775年欧拉对脉搏波的传播进行了研究。直至1914年,其他研究者开始强调了动脉顺应性和血液的惯性对脉搏的影响。本文主要从临床生理学的角度作一概述。一、脉搏波传播的概念: 祖国医学认为,“心者,生之本……其充在血脉”。心脏是一个搏动泵,血液随心室收缩而间歇地流入动脉。心脏每舒缩一次,在动脉系统中就产生一个脉搏波。心室收缩射血时,血液流向血管使动脉扩张;心室舒张而停止射血时,动脉便弹性回缩,使血压时高时低产生脉动,动脉管壁也时张时缩发生振荡,这种脉动能量犹如水面的涟漪波及和影     

红丝线草醇提水转溶物对急性高血压猫心功能和血流动力学的影响

本文报道红丝线草醇提水转溶物（ＯＬ－Ｗ）对急性高血压猫心功能和血流动力学的影响。实验结果表明：两种剂量（ＬＤ＿５０的１／５０、ＬＤ＿５０的１／３０）的ＯＬ－Ｗ静脉注射给药后：（１）可降低ＬＶＰ、ＭＢＰ、ＤＢＰ、ＳＢＰ、ＴＰＶＲ，均有非常显著性差异（Ｐ＜０．０１）。（２）降低ＬＶＷ，ＬＶＷＩ、ＬＶＳＷ、ＬＶＳＷＩ、ＴＴＩ、ＴＴｌ×ＨＲ，Ｐ值均＜０．０１。（３）改善心肌舒张性，包括缩短Ｔ，具有统计学意义（Ｐ＜０．０１）。综上所述，ＯＬ－Ｗ能显著降低高血压猫的血压，且能改善心室舒张功能。     

培养的大鼠血管平滑肌细胞血管紧张素Ⅱ受体的基因表达及调节

在培养的自发性高血压大鼠（ＳＨＲ）和正常血压ＷＫＹ大鼠的主动动脉平滑肌细胞（ＡＳＭＣ）模型，应用Ｎｏｒｔｈｅｒｎ杂交和逆转录－聚合酶链反应（ＲＴ－ＰＣＲ）技术，分别检测ＡＳＭＣ中碱性成纤维细胞生长因子（ｈＦＧＦ）和血管紧张素Ⅱ（ＡＮＧⅡ）Ｉ型受体（ＡＴ１Ｒ）的基因表达。结果表明：ＳＨＲＡＳＭＣ中ｈＦＧＦ基因的基础表达和ＡＮＧⅡ刺激后的表达水平元旦明显高于ＷＫＹ大鼠；ｂＦＧＦ（１０ｎｍ／ｍｌ）对两种     

体外模拟心血管系统血液动力学性能分析

为研究人工心脏和心血管系统之间的血液动力学作用机制．根据弹性腔模型建立了一套能反映血液动力学特性的体外血液循环模拟实验装置，测试血液动力学参量与心室后负荷（即外周力R和动脉顺应性C）以及每搏心输出量Vs，心动周期T和心室收缩时间间隔Ts，前负荷等六个参量之间的相互关系．通过改变六个参量中的某一个参量而固定其余参量，测试这个参量对动脉血压及流量的影响情况。实验结果与生理情况和数学模型分析相符合。压力和流量波呈脉动性，与真实生理波形相似。整个模拟装置能够反映血液动力学特性。     

双腔主动脉内气囊反搏的血流动力学影响的研究

我们的实验结果表明双腔主动脉内气囊（ＤＩＡＢ）反搏的效果要优于单腔主动脉内气囊（ＳＩＡＢ）反搏的。它明显地改善血流动力学参数,进而提高了反搏的功效。也未发现双腔主动脉内气囊进行反搏会对肾脏的血流动力这参数产生不良影响。在对比肾动脉去神经前后主动脉内气囊反搏的结果,发现反搏时产生的脉动会对血管神经系统产生刺激,从而降低肾血管局部的阻力。这是当气囊进行反搏时,使肾脏血液循环得以改善的最重要因素。     

光动力学疗法对大鼠W256移植瘤的生长和GSH—PX活性的影响

用光动力学疗法（ｐｈｏｔｏｄｙｎａｍｉｃｔｈｅｒａｐｙ，ＰＤＴ）对Ｗ２５６移植瘤进行治疗，并观察Ｗ２５６移植瘤的生长速度和检测大鼠血和肝组织中谷胱甘肽过氧化物酶（ＧＳＨ－ＰＸ）的活性，结果如下：（１）接受ＰＤＴ治疗组大鼠Ｗ２５６移植瘤生长缓慢Ｐ〈０．０５），（２）接受ＰＤＴ治疗组大鼠血和肝组织中的ＧＳＨ－ＰＸ活性显著低于肿瘤对照组大鼠（Ｐ〈０．０１），而肿瘤对照组大鼠血和肝组织中ＧＳＨ－ＰＸ活性又     

高血压鼠和正常鼠血管的生物力学特性

本文就原发性高血压大白鼠（ＳＨＲ）和正常京都纯种大白鼠（ＷＫＹ）作对照，测定其胸主动脉的管径、厚度、应力－应变和断裂时的相对伸长度，在拉格郎日（Ｌａｇｒａｎｇｉａｎ）意义下讨论应力应变，并按冯元桢－维拉伸理论，从实验得出经验公式：ｄＴ／ｄλ＝α（Ｔ－β）＝αＴ－Ｅ０，以确定高血压和老龄化血管生物力学性能的变化。发现：不仅京都鼠血管的相对伸长率大于高血压鼠，而且从各年龄观察，幼龄的血管相对伸长率大于老龄者，高血压和老龄者的血管弹性模量相对大；在低应力区时，高血压和老龄化的胸主动脉弹性差，弹性模量大，刚度大；而在高应力区时，两者相差不多。这可能是高血压或老龄鼠血管的弹性纤维减少的缘故。     

系统性硬化病血管内皮活性因子测定的临床意义

目的：从蛋白分子水平探讨血管内皮活性因子同系统性硬化病的关系。方法：选择４２例ＳＳｃ病人采用放射免疫测定法检测血浆内皮素（ＥＴ）、血栓素Ｂ２（ＴＸＢ２）、６－酮－前列腺素Ｆ１α（６－Ｋ－ＰＧＦ１α）,采用Ｇｒｉｓｓ方法检测血浆一氧化氮（ＮＯ）水平,关免疫法检测细胞间粘附分子－１（ＩＣＡＭ－１）、选择素（Ｐ－Ｓ）。结果;所有ＳＳＣ患者均存在高ＥＴ、ＴＸＢ２、ＩＣＡＭ－１、Ｐ－Ｓ血症,存在低ＮＯ、６－     

A review of wave mechanics in the pulmonary artery with an emphasis on wave intensity analysis

Mean pulmonary arterial pressure and pulmonary vascular resistance (PVR) remain the most common haemodynamic measures to evaluate the severity and prognosis of pulmonary hypertension. However, PVR only captures the non‐oscillatory component of the right ventricular hydraulic load and neglects the dynamic compliance of the pulmonary arteries and the contribution of wave transmission. Wave intensity analysis offers an alternative way to assess the pulmonary vasculature in health and disease. Wave speed is a measure of arterial stiffness, and the magnitude and timing of wave reflection provide information on the degree of impedance mismatch between the proximal and distal circulation. Studies in the pulmonary artery have demonstrated distinct differences in arterial wave propagation between individuals with and without pulmonary vascular disease. Notably, greater wave speed and greater wave reflection are observed in patients with pulmonary hypertension and in animal models exposed to hypoxia. Studying wave propagation makes a valuable contribution to the assessment of the arterial system in pulmonary hypertension, and here, we briefly review the current state of knowledge of the methods used to evaluate arterial waves in the pulmonary artery.     

Physiological and pathophysiological implications of ventricular/vascular coupling

The purpose of this paper is to consider “ideal” ventricular/vascular coupling, and how this may be manifest in the time domain and in the frequency domain. The paper will also consider how such “ideal” coupling is achieved, and how it might be disturbed. The arterial system plays a crucial role in ventricular/vascular coupling since it separates the smallest vessels where flow is almost perfectly continuous from the ventricle, whose output is intermittent. Ventricular/vascular coupling can be assessed from measurements of pressure and flow in the ascending aorta (AA) (for left ventricle/systemic circulation), and in the main, pulmonary artery (MPA) (for right ventricle/pulmonary circulation). Ideal coupling is manifest as low pressure fluctuation in AA and MPA. Low pressure fluctuation results in pressure during systole being only slightly greater than pressure throughout the whole cardiac cycle, and pressure during diastole being only slightly less. This is desirable because pressure during systole determines ventricular output (when inotropic state and ventricular filling are constant), and ventricular metabolic requirement, while pressure during diastole in AA is a major determinant of coronary blood flow. In the frequency domain, “ideal” coupling is manifest as a correspondence between minimal values of impedance modulus in AA and MPA with maximal values of flow harmonics in AA and MPA, respectively. Factors responsible for “ideal” coupling have been identified as high distensibility of proximal arteries (with decreasing distensibility in peripheral arteries), wave reflection at arterial terminations, and a “match” between heart rate on the one hand and arterial length and wave velocity on the orther. This favourable “match” results in the heart operating for both systemic and pulmonary circulations close to a node of pressure and antinode of flow; this match is improved under conditions which simulate flight and fight. While ventricular/vascular coupling appears to be close to ideal in most large mammals, it appears to be less than ideal in adult humans and some small mammals including guinea pigs, rats, and mice. The cause for mismatch in small mammals is unclear. In humans however, finding are attributable to progressive arterial degeneration which is known to commence in childhood and is apparent in the elderly as dilated tortuous arteries, high pulse pressure, and high likelihood of developing ventricular failure.     

The role of usable length in the compliance measurement of vascular prostheses

In this study we investigated the dependence of the mechanical properties and in particular of the radial compliance of a vascular prosthesis as a function of its usable length. Radial compliance was measured at 60 bpm and in the pressure range 80-120 mmHg. Starting from compliance measurements a simple model was used to calculate the pulse wave velocity and the reflection coefficients between 6 mm and 8 mm grafts (knitted and woven) with iliac and subclavean artery of similar diameter. The results provide an indication of the influence of usable length on the compliance and diameter mismatch at the anasthomosis between graft and host artery.     

Coupling pediatric ventricle assist devices to the Fontan circulation: simulations with a lumped-parameter model

In pediatric ventricular assist device (VAD) design, the process of matching device characteristics and dimensions to the relevant disease conditions poses a formidable challenge because the disease spectrum is more highly varied than for adult applications. One example arises with single-ventricle congenital defects, which demand palliative surgeries that create elevated systemic venous pressure and altered pulmonary hemodynamics. Substituting a mechanical pump as a right ventricle has long been proposed to eliminate the associated early and postoperative anomalies. A pulsatile lumped-parameter model of the single-ventricle circulation was developed to guide the preliminary design studies. Two special modules, the pump characteristics and the total cavopulmonary connection (TCPC) module, are introduced. The TCPC module incorporates the results of three-dimensional patient-specific computational fluid dynamics calculations, where the pressure drop in the TCPC anastomosis is calculated at the equal vascular lung resistance operating point for different cardiac outputs at a steady 60/40 inferior vena cava/superior vena cava flow split. Preliminary results obtained with the adult parameters are presented with no ventricle remodeling or combined larger-size single ventricle. A detailed literature review of single-ventricle function is provided. Coupling a continuous pump to the single-ventricle circulation brought both the pulmonary and systemic venous pressures back to manageable levels. Selected VADs provided an acceptable cardiac output trace of the single left ventricle, after initial transients. Remodeling of the systemic venous compliance plays a critical role in performance and is included in this study. Pulsatile operation mode with rotational speed regulation highlighted the importance of TCPC and pulmonary artery compliances. Four different pumps and three patient-specific anatomical TCPC pathologies were studied. Magnitudes of the equivalent TCPC resistances were found to be comparable to the vascular resistances of the normal baseline circulation, significantly affecting both the VAD design and hemodynamics.     

Influence of Moderate Vasoconstriction on the Wave Reflection Properties of the Pulmonary Arterial Bed

Increased transmural pressure in the pulmonary arterial bed may reduce vascular input impedance and reduce hydraulic power linked to pulsatile blood flow. Vascular impedance and pulsatile hydraulic power (Wp) levels of isolated perfused rabbit lungs were compared after similar rises of pulmonary arterial pressure (PAp), induced either by vasoconstriction or by left atrial pressure (LAp) elevation. Resulting Wp levels were significantly smaller after vasoconstriction than LAp elevation. Wp showed a minimum level at physiologic PAp (about 20 cm H₂O) irrespective of the cause of PAp elevation. Pressure pulse wave reflection coefficient (Γ) was calculated for control and test situations, and was found to be approximately doubled after vasoconstriction. Only minor changes in Γ were found after LAP elevation. Accordingly, moderate vasoconstriction (resulting PAp?20 cm H₂O) caused a backward traveling pressure wave of high amplitude, appearing in counter-phase to the forward pressure wave at the input site. The total pressure wave amplitude was thereby markedly lowered, resulting in a reduced Wp level. We assume that this effect of moderate vasoconstriction may be one reason for the existence of vascular smooth muscles in the pulmonary arteries.     

Hydromechanical simulation of systemic circulation

A hydromechanical model is developed for the simulation of the arterial systemic circulation. The geometry and elastic properties of arteries, the pulse-rate and stroke volume of the left ventricle, the design of peripheral resistances and the viscosity of the model fluid are approximated to physiological conditions. The parameters, pulse rate, stroke volume, pulse volume, elasticity of arteries, as well as peripheral resistances, are independent variables.     

Constrictive and restrictive pulmonary hypertension in the newborn and infant

The normal pulmonary circulation is constricted at birth and, as judged by its low arterial density, is relatively more restricted than in the older infant and child. During adaptation to air breathing, pulmonary arterial dilatation occurs rapidly, but also the compliance of the resistance arterial segment increases. In the fetus and newborn, the resistance segment is proximal to the respiratory or alveolar surface. Further expansion of the pulmonary vascular bed occurs by growth in size of lumen diameter of existing arteries and growth of new ones. Multiplication of alveoli and arteries is relatively dissociated--alveolar density can increase normally without normal vascular multiplication. Persistent pulmonary hypertension of the newborn occurs because of (1) lung hypoplasia associated with hypoplasia of the vascular bed, usually affecting both size and number of units, (2) abnormal muscularization of intraacinar arteries before birth, causing restriction of vascular volume, (3) failure of the adaptation programs, and (4) hyperreactivity. Immaturity of the circulation is apparent as hyperreactivity or "twitchiness": this can be superimposed on each of the other types. A hyperirritable vascular bed can cause a labile and then a fixed pulmonary hypertension that does not respond to dilators.     

Pulmonary blood volume and interventricular circulation time in physically trained and untrained subjects

Summary Resting pulmonary plasma and blood volumes (PPV and PBV), interventricular circulation time (IVCT), cardiac and stroke index (CI and SI), heart rate (HR), total plasma and blood volumes (PV and BV) were determined in athletes (two male groups representing different types of sport activities, and one female group) and compared with those of non-athletes (one male and one female group).In addition to high maximal aerobic power, the athletes were characterized by greater SI, BV and PV and lower resting HR than non-athletes. PPV and PBV were significantly larger and IVCT significantly longer in the trained than in the untrained groups, probably reflecting an improved capacity of the pulmonary circulation. PPV as per cent of PV was almost equal in all the groups, indicating the same distribution of plasma between the pulmonary and systemic circulation. The data also indicate that total blood volume is an important determinant of the magnitude of the pulmonary vascular bed. The increased volume of flowing blood and increased stroke volume in athletes probably allows for a reduction in flow velocity and thereby a reduction in kinetic energy.     

Increased reversal and oscillatory shear stress cause smooth muscle contraction-dependent changes in sheep aortic dynamics: role in aortic balloon pump circulatory support

Aims: The intra‐aortic balloon pumping (IABP) changes pressure and increases the aorta shear stress reversal (SS_R) and oscillatory (SS_O) components. Hence, IABP‐dependent changes in aortic biomechanics would be expected, because of vascular smooth muscle (VSM) tone (i.e. flow‐induced endothelium‐dependent response, related to SS_R and SS_O variations) and/or pressure changes. To characterize: (i) the IABP effects on the aortic and global (systemic circulation) biomechanics, analysing their dependence on pressure and VSM basic tone changes and (ii) the relation between the SS_R and SS_O and the aortic biomechanical changes associated with the VSM tone variations. Methods: Aortic flow, pressure and diameter were measured in eight sheep during basal, augmented and assisted beats (1 : 1 and 1 : 2 IABP modalities). Calculations: (i) aortic effective and isobaric elasticity, viscosity, circumferential stress, pulse wave velocity, shear stress and buffer and conduit functions, (ii) peripheral resistance, global compliance, reflection coefficient and wave propagation times and (iii) the relation between SS_R and SS_O and biomechanical changes associated with variations in the aortic VSM tone. Results: Augmented and assisted beats showed: global VSM relaxation pattern (reduced peripheral resistance and reflection coefficient; increased propagation times) and local VSM contraction pattern (increased viscosity; reduced diameter, elasticity and circumferential stress), associated with SS_R and SS_O, levels and changes. The vascular changes reduced the ventricle afterload determinants, increased the vascular buffer performance and kept the conduit capability. Conclusion: In addition to pressure‐dependent changes, IABP determined biomechanical changes related to variations in the VSM tone. The increased SS_R and SS_O were associated with the aortic VSM contraction pattern and biomechanical changes.     

Central cardiovascular dynamics of ducks.

Blood pressures and flows have been recorded from the heart and arterial arches of ducks in order to present a complete picture of central hemodynamics in an avian species. An attempt has also been made to define the characteristics of the avian central circulation in terms of either "windkessel", or wave-transmission models. Mean arterial pressure (143 plus or minus 2.2 mmHg) and cardiac output (219 plus or minus 7ml/kg per min) were high compared with those of similarly sized mammals, although therewas no evidence of elevated pulmonary pressures, perhaps because of the unusual structure of the avian lung. Only 25% of the total systemic flow was distributed by the aorta, the remainder supplying the wing, flight muscles, and head via the brachiocephalic arteries. The contours of central pressure and flow waves ressembled those recorded inmammal except that significant circulation impedance modulus graphs indicated that resistance to pulsatile flow fell sharply to a minimum of 1/30th the DC value at 9-12 Hz. Flow led pressure at frequencies below 9-12Hz and pressure led flow at higherfrequencies. Impedance modulus in the pulmonary circulation fell to one-half the DC value and remained constant over a wide range of frequencies with pressure and flow being in a phase at all frequencies. Aortic pulse wave velocity varied with position inthe aorta as did the pressure pulse profile: these factors obviously limit the applicability of a windkessel model to the avian circulation.