Effects of Vessel Wall Elasticity on Blood Flow

通过体外和体内实验，分别研究了血管壁弹性对血流特性的影响，重点研究了血流湍流的产生和发展以及微血管中血流脉冲的传播。在体外实验中，用激光多普勒风速仪测量了完全发育的脉动流（除平均流外的正弦流）。得到了不同脉动流条件下的速度波形和管截面内的速度分布。在非湍流状态下，速度波形和速度曲线与理论预测吻合较好。对于湍流过渡，记录在固定频率和振幅的脉动下增加平均雷诺数时的中心线速度。在减速阶段，当平均雷诺数大于一个临界值即过渡雷诺数时，流动变得紊流。在调制雷诺数为880、频率参数为5.9的条件下，透射离子雷诺数为2400。考虑稳态流动的传递雷诺数为2000，表明在脉动条件下流动是稳定的。在体内实验中，利用光纤激光多普勒风速显微镜（FLDAM）研究了血流脉冲在大鼠肠系膜微血管网络中的传播。测定小动脉、毛细血管和小静脉的平均流速、脉动幅度、微血管流量相对于颈动脉压力的相位滞后。在微血管理想模型的基础上，分析了平均流量、流量幅值和相位滞后的动静脉分布。自发性高血压大鼠（SHR）与正常对照组大鼠（WKY）的分布差异可以通过SHR小动脉的稀疏性从理论模型上解释。同时测定了血流脉冲在小动脉中的传播速度。由传播速度估计的血管壁弹性模量在2x10^6 ~ 2x10^7 dyn/cm^2之间，与大动脉的弹性模量在同一数量级。少

In vitro and in vivo experiments were conducted to study the effects of the vessel wall elasticity on the blood flow characteristics focusing on thegeneration and development of blood flow turbulence and on the propagation of flow pulse in microvessels, respectively.In in vitro experiments, a fully developed pulsatile flow (sinusoidal flow in addition to mean flow) was measured by a laser-Doppler anemometer. The velocity waveforms and the velocity profiles in the tube cross-section were obtained under various conditions of pulsatile flow. When the flow was not turbulent, the velodcity waveforms and the velocity proviles agreed well with the theoretical predictions. Regarding the turbulence transition, the centerline velocity was recorded as the mean Reynolds number was increased with a fixed frequency and amplitude of pulsation. The flow became turbulent in the deceleration phase when the mean Reynolds number was larger than a critical value, the transition Reynolds number. The transis … More ion Reynolds number was 2400 at the modulation Reynolds number of 880 and the freqyency parameter of 5.9. Considering the transision Reynolds number of steady flow was 2000, it means that the flow is stabilized under the pulsatile condition.In in vivo experiments, propagation of flow pulse was studied in microvascular networks of rat mesentery by a fiber-optic laser-Doppler anemometer microscope (FLDAM). The mean flow rate, amplitude of the flow pulsation, phase lag of the microvascular flow relative to the carotid arterial pressure were determined in arterioles, capillaries and venules. The arterio-venous distributions of the mean flow, flow amplitude and phase lag were analyzed based on an idealized model of the microvasculature. The difference observed in the distributions between spontaneously hypertensive rats (SHR) and normotensive control rats (WKY) were explained from the theoretical model by the rarefaction of small arterioles in SHR.Thepropagation velocity of flow pulse was also measured in arterioles. The elastic modulus of the vessel wall estimated from the propagation velocitywas in the range from 2x10^6 to 2x10^7 dyn/cm^2, which was in the same order of the elastic modulus for large arteries. Less