通脉饮对大鼠急性血瘀证血液流变性的影响

采用皮下注射大剂量肾上腺素加寒冷刺激的方法复制大鼠急性血瘀证模型，观察了通脉饮对该模型血液流变性的影响。结果表明：通脉饮对急性血瘀证血液流变性有明显改善作用。提示：通脉饮可能对预防冠心病及高粘血症有作用     

三七对两种大鼠血浆凝血过程的血液流变学模型参数的影响

目的有人用旋转黏度计在恒定的低切变率下测定了抗凝血样复钙后的切应力随时间变化的曲线。笔者针对这一方法提出了一种凝血过程的血液流变学理论模型，本研究试图寻求并分析2种大鼠血浆（正常血浆、富血小板血浆）在给予三七皂苷前后其各自模型参数的差异。方法应用模型拟合实验数据，比较所得2种大鼠血浆给予三七皂苷前后其各自的模型参数，从中找出差异。结果模型参数中的大部分没有变化，只有少数几个参数发生变化，有的甚至变化很大。结论模型拟合出的各种模型参数均有明确的血液流变学意义，通过模型参数的变化可以分析出血浆受药物影响前后其凝固性能的差异。     

脑循环血液动力学研究:Willis环定常流力学模型

脑循环系统因为Ｗｉｌｉｓ环的存在而具有其特殊的血液动力学特性。脑Ｗｉｌｉｓ环是一个具有四端输入的网络系统。本文依据人体Ｗｉｌｉｓ环的解剖结构，提出一个模拟脑循环定常流的集中参数模型及其控制方程。通过对正常人和几种疾病患者的脑循环模拟发现，理论模型提供的结论和生理病理现象完全一致。本模型将为进一步研究Ｗｉｌｉｓ环的血液动力学特性及检测脑血管血液动力学参数提供新的方法。     

测量生物组织血液灌注率的ATM模型及其误差分析

采用脉冲衰减法可以测量生物组织的血液灌注率。本研究给出了脉冲衰减法测量时探头平均温度的理论解（ATM模型）。通过分析温度测量误差及探头输入功率测量误差引起的血液灌注率测量误差，以及测量时的模型误差，比较了ATM模型与现有的PSM模型（Point Source Model）及SSM模型（Spherical Source Model）的测量精度。结果表明，对三种模型，由温度测量误差及探头输入功率测量误差引起的血液灌注率测量误差均大致相等；而采用ATM模型测量时的模型误差比PSM模型和SSM模型要小；测量时刻以脉冲后13s～17s为宜；测量时应尽量选用几何尺寸比较小的生物探头；对于小血液灌注的测量，采用ATM模型更为有利。     

脑Willis环动力学参数计算与临床应用

在已有的脑Willis环研究的基础上，建立了反映脑循环血液脉动特性的集中参数模型并给出了参数求解方法，通过对30例临床数据的计算发现理论值与大部分疾病诊断结果相吻合，这不仅说明模型是符合生理实际的，还说明模型参数的求解方法在临床上是切实可行的。     

血液流变性改变对电学特性的影响

本文根据血液三元件电模型，介绍了红细胞聚集，解聚和红细胞在流场中的取向、变形，以及血浆蛋白等血液流变学因素的改变对血液电学特性的影响。     

红细胞非惯性升力对血液流动的影响

目的为准确模拟血流,研究红细胞变形性对血液流动的影响。方法基于血液流变特性和红细胞力学特性分析,对现有血液两相流流动模型进行改进,改进模型中考虑了易变形红细胞受剪切流场或血管壁面作用而产生的非惯性升力的影响。利用改进模型对多个不同直径血管内的血液流动进行模拟。结果由红细胞所受非惯性升力导致的径向运动对血管内红细胞体积分数、运动速度分布有明显影响;当血管直径为0.1~3.0 mm时,用改进模型得到的血液相对黏度的模拟值与测量值接近。结论非惯性升力是血流呈现Fahraeus-Lindqvist效应的主要原因之一。考虑非惯性升力的改进模型可以准确模拟血液流动,为循环系统诊疗机制和细胞分选等过程的模拟提供更为准确的方法。     

急性坏死性胰腺炎血液流变学改变与治疗

目的通过纠正血液流变学异常，以期阻断胰腺炎不断恶化的病理过程。方法胰胆管注射牛磺胆酸制备大鼠急性胰腺炎模型，术后随机分别输注葡聚糖、生理盐水及葡聚精＋地塞米松。总液量控制在 ６ｍｌ／ｈ，共治疗３小时后，检测血液流变学指标、红细胞脆性试验和胰腺病理学改变。结果急性胰腺炎大鼠全血粘度、血浆粘度、红细胞压积均显著升高，纤维蛋白原降低，红细胞脆性增加。葡聚糖可显著降低急性胰腺炎大鼠的血液粘度、红细胞压积和红细胞脆性，并降低胰腺组织的炎症程度。结论 急性胰腺炎时血液流变学出现显著改变，葡聚糖可通过纠正血液流变学异常降低胰腺组织的炎症程度。     

红细胞非惯性升力对血液流动的影响

目的 为准确模拟血流,研究红细胞变形性对血液流动的影响。方法 基于血液流变特性和红细胞力学特性分析,对现有血液两相流流动模型进行改进,改进模型中考虑了易变形红细胞受剪切流场或血管壁面作用而产生的非惯性升力的影响。利用改进模型对多个不同直径血管内的血液流动进行模拟。结果 由红细胞所受非惯性升力导致的径向运动对血管内红细胞体积分数、运动速度分布有明显影响;当血管直径为0.1~3.0 mm时,用改进模型得到的血液相对黏度的模拟值与测量值接近。结论 非惯性升力是血流呈现Fahraeus-Lindqvist效应的主要原因之一。考虑非惯性升力的改进模型可以准确模拟血液流动,为循环系统诊疗机制和细胞分选等过程的模拟提供更为准确的方法。     

门静脉高压症经颈静脉肝内门体分流术(TIPS)血液动力学分析

经颈静脉肝内门体分流术（TIPS）是治疗门静脉高压症的有效手术之一。本文提出了一个集中参数模型对TIPS进行血液动力学分析。首先根据门脉高压的前向血流学说和后向血流学说，计算了门静脉系统血液动力学参数，然后计算了TIPS术后门静脉系统血液动力学参数的变化，并详细分析讨论了这些血液动力学参数随肝硬变梗阻程度的变化，以及TIPS分流道阻力对它们的影响。结果表明所得结果和临床所测参数吻合较好，该模型可进一步应用于门脉高压症和其它分流术血液动力学机理研究，并为临床应用提供参考。     

Quantitative evaluation of the systemic arterial bed by parameter estimation of a simple model

The parameters of a simple model (r-L-C-R) of the systemic circulation are estimated from aortic root pressure and flow, which are either simulated by a complex model of the systemic circulation or measured in dogs. This model contains one additional parameter (inductance L) as compared with the r-C-R model proposed by Westerhof; it allows for a better representation of the input impedance of the complex model and of the systemic circulation in dog, resulting in meaningful values for the parameters r, C, R. Because there is a good relation between C and the sum of the compliances of the complex model, and because C varies in the direction of the expected changes in compliance following angiotensin and sodium nitroprusside administration in dogs, C appears to be a valid estimate of the total systemic arterial compliance. The good relation between r and the characteristic impedance in the complex model or in the upper thoracic aorta of the dog indicates that r is a good measure of the characteristic impedance. The r-L-C-R model therefore appears to provide a better characterisation of the left ventricular afterload than the r-C-R model. The identification of this r-L-C-R model also permits a more convenient quantification of the afterload than the classical computation of input impedance.     

Evaluation of a lumped parameter model for isolated working rat hearts

When a mechanical model of the rat aortic input impedance is perfused with a pulsatile pump, the computed values of the impedance components vary linearly with flow rate and are interactive. When the model is perfused by an isolated rat heart, the total load upon the left ventricle consists of the model and coronary impedances in parallel. Adenosine triphosphate induces changes in coronary impedance, and the redistribution of cardiac output from the model to the coronary circulation causes flow-related changes in the model impedance. Thus, the mechanical model does not provide a constant load for the isolated heart, because of variations in both the model and coronary impedances.     

Evaluation of a lumped parameter model for isolated working rat hearts

When a mechanical model of the rat aortic input impedance is perfused with a pulsatile pump, the computed values of the impedance components vary linearly with flow rate and are interactive. When the model is perfused by an isolated rat heart, the total load upon the left ventricle consists of the model and coronary impedances in parallel. Adenosine triphosphate induces changes in coronary impedance, and the redistribution of cardiac output from the model to the coronary circulation causes flow-related changes in the model impedance. Thus, the mechanical model does not provide a constant load for the isolated heart, because of variations in both the model and coronary impedances.     

The influence of mock circulation input impedance on valve acceleration during in vitro cardiac device testing

For a mechanical heart valve, a strong spike in pressure during closing is associated with valve wear and erythrocyte damage; thus, for valid in vitro testing, the mock circulation system should replicate the conditions, including pressure spikes, expected in vivo. To address this issue, a study was performed to investigate how mock circulation input impedance affects valve closure dynamics. A left ventricular model with polyurethane trileaflet inflow valve and tilting disc outflow valve was connected to a Louisville mock circulation system, which incorporates 2 adjustable flow resistors and 2 compliances. In the study, 116 cases matched zero frequency modulus well (982-1147 dyn x s/cm), but higher harmonics were purposely varied. Acceleration measured at the outflow valve ring (42.4-89.4 milli-Gs) was uncorrelated with impedance error (74.1-237 dyn x s/cm relative to target impedance), but was correlated with end-systolic impedance (1082-1319 dyn x s/cm) for cases with high zero frequency modulus, which exhibited just less than full ejection. These differences demonstrate that mock circulation response affects the magnitude of the closing spike, indicating that control of this parameter is necessary for authentic testing of valves. Correlation of acceleration to end-systolic impedance was weak for low zero frequency modulus, which tended toward full or hyperejection, reinforcing common laboratory observations that valve closing also depends on ventricular operating conditions.     

Development of a hydraulic model of the human systemic circulation

Physical and numeric models of the human circulation are constructed for a number of objectives, including studies and training in physiologic control, interpretation of clinical observations, and testing of prosthetic cardiovascular devices. For many of these purposes it is important to quantitatively validate the dynamic response of the models in terms of the input impedance (Z = oscillatory pressure/oscillatory flow). To address this need, the authors developed an improved physical model. Using a computer study, the authors first identified the configuration of lumped parameter elements in a model of the systemic circulation; the result was a good match with human aortic input impedance with a minimum number of elements. Design, construction, and testing of a hydraulic model analogous to the computer model followed. Numeric results showed that a three element model with two resistors and one compliance produced reasonable matching without undue complication. The subsequent analogous hydraulic model included adjustable resistors incorporating a sliding plate to vary the flow area through a porous material and an adjustable compliance consisting of a variable-volume air chamber. The response of the hydraulic model compared favorably with other circulation models.     

Umbilical flow distribution to the liver and the ductus venosus in human fetuses during gestation: an anatomy-based mathematical modeling

The partitioning of umbilical vein blood flow between fetal liver and ductus venosus may be an indicator of the fetal well-being, because the goal of the ductus venosus is to supply oxygen and nutrients to heart and brain. Both distribution and blood flow rate of the umbilical vein are functions of the local vascular impedances that, in turn, depend on the anatomical features of the related vessels. In order to investigate the venous blood flows in human fetuses during a normal gestation, a simple lumped parameter mathematical model was developed on the basis of some information achievable by ultrasonographic techniques. Particularly, the diameter and length of umbilical vein and ductus venosus and the volume of the liver were used to derive the vascular impedances. Three different impedance models were adopted for the umbilical vein, the ductus venosus and the hepatic circulation. A linear model described viscous hydraulic dissipations through the umbilical vein, while a quadratic pressure-flow relationship was used for the ductus venosus due to the irregular local hemodynamics at its inlet. Finally, the equivalent impedance of the whole hepatic network was related to the hepatic volume assuming a tree-like, symmetric and self-similar fractal geometry. The hepatic vascular resistances predicted according to the fractal analysis were quite consistent with some experimental measurements in fetal lambs. In agreement with clinical observations, the model predicted blood flows through the ductus venosus and umbilical vein increasing (from about 25 to 75 ml/min and from about 45 to 370 ml/min, respectively) throughout the gestation (20-40 weeks), while the flow fraction shunted via the ductus venosus diminishes (from about 50 to 20%).     

Wave transmission and input impedance of a model of skeletal muscle microvasculature

We analyzed wave transmission properties and input impedance of a microvascular network model. The model, derived from rat spinotrapezius muscle and previously described and validated by other investigators for steady pressure-flow relations, was expanded to include pulsatile phenomena. Microvessels are considered purely elastic, with compliances a function of vessel type; viscous dissipation follows Poiseuille's law. Linear and nonlinear results are presented. In the nonlinear case, shear rate-dependent viscosity of blood and transmural pressure-dependent vascular diameters were calculated and small signal perturbations were imposed around several working points. We investigated effects on input impedance of physiological variability of network parameters and structure: distribution of capillary diameters, capillary segment length, and presence or absence of cross-connecting capillaries. Results show that although wave transmission properties are complex, input impedance is simple. Apparent wave speeds differ substantially from phase velocities and change markedly from branch to branch; pressure and flow waves appear to travel at different speeds. These features result from the mesh-like structure of the network and the prominence of reflection at branchpoints. Input impedance displays a similar form under all conditions: Magnitude is a monotonically decreasing function of frequency, and phase decreases from 0 to approximately −45°. Consideration of the characteristic impedance of a microvessel leads to modification of the three-element Windkessel as a reduced model of the observed input impedance.     

Multivariate autoregressive modelling combined with transcephalic electrical impedance: method to relate neonatal systemic circulation and respiration to cerebral circulation

We studied the pulsatile component of cerebral circulation with transcephalic electrical impedance (ΔZ) in six preterm newborns, three of whom had severe cerebral bleeding, peri-intraventricular haemorrhage (PIVH). The transcephalic electrical impedance ΔZ signal, ECG, arterial blood pressure, (aBP) and respirogram were recorded on analogue magnetic tape for 30 min. Artefact-free stationary segments (lasting for 2 min) of the four signals were digitised. A digital multivariate autoregressive (MAR) model was used to study frequency-specific variability in the signals and to quantify interrelations between the variabilities of ΔZ, HR, aBP and respiratory signals. MAR modelling describes a system where all the signals simultaneously explain each other. The inherent variability of ΔZ was lower and the influences of respiration and aBP on ΔZ significantly greater in infants with severe PIVH than in controls. These changes were observed at high frequencies corresponding to respiration and heart rate. This may be interpreted as a marker of pressure passivism in the cerebral circulation following PIVH. We conclude that in preterm babies the application of MAR modelling, together with transcephalic impedance, may be a new, helpful and quantitative method for the study of simultaneous interrelations between variables of cerebral and systemic circulations and respiration.     

心血管系统体循环后负荷的集中参数模型

本文给出一种新的模拟心血管系统体循环后负荷的三弹性腔九元件集中参数模型。它能令人满意地拟合升主动脉输入阻抗的生理曲线，且结构简单，调试方便，各元件具有明确的生理意义，其取值也在合理的生理范围内。本文还研究了模型中各参数对升主动脉输入阻抗的影响。本模型可做为心血管系统体循环模拟研究的较为理想的后负荷。     

脑循环动力学模型与血管输入阻抗模拟

本文提出了一个脑循环血液动力学模型，在模型中不仅考虑了血管弹性、阻力和惯量等动力学参数，而且还考虑了交通动脉的血管代偿功能。通过模型控制方程求解得到了颈动脉和椎动脉的输入阻抗，理论和实验结果完全相一致。模拟结果表明：当颈动脉或推动脉动力学参数变化时，它不仅影响同侧的动脉阻抗，而且还影响到对测血管床。这提示，颈动脉或推动脉输入阻抗不仅和自身系统血管特性有关，而且还受其它循环的影响，有时这种影响还是显著的。