CARDIOPULMONARY GEOMETRY AND BLOOD FLOW IN GROWING LAMBS

无创检测肺血流速度的潜力 脉冲多普勒超声激发了人们对人际关系的兴趣 血流速度模式和肺血流动力学异常之间的关系。 不幸的是，临床和实验研究发现 报告的特征与肺异常有很好的相关性 在正常受试者中经常观察到压力和/或阻力。为 例如，沿右后壁的显著回流 肺动脉高压患者的肺干，已被 归因于主肺动脉的曲率增强，也 在正常的羔羊、狗和人类身上也观察到了这种情况。动物的相似性 活体速度分布与脉动流研究中获得的分布 在弯曲的管子中，几何图形扮演着与 血流动力学在确定血流速度模式中的作用。因此，理解 1)正常成熟与几何的关系；20)正常成熟与几何的关系 几何学和流体动力学是诊断的关键技术 婴幼儿先天性心脏病引起的体液动力学改变 肺脏几何形状会迅速改变的儿童， 要有所改进。使用从1日龄到1日龄的一系列发育中的羔羊 这项研究将通过在体内进行实验来解决这些问题， 原位实验和体外实验。(A)在体内阶段，速度 将使用以下方法获得主和分支肺动脉的轮廓 20 MHz脉冲多普勒仪。收集的数据将用于预测 正常或年龄段的二维和三维速度分布和输入阻抗 并验证在体外测定的图谱的真实性 以后的研究。(B)右心室和近端肺的管型 动脉将在正常生理压力下原位制作。这个 管型，揭示了漏斗瓣下区域的重要性， 可以进行CT扫描，并将其结构提交到计算机内存中，从 可以重建哪些二维和三维图像。算法将 用于量化主干、流量的曲率和扭矩 分隔器偏移、分叉角度、锥度和线束段尺寸。数据 所获得的数据将用于量化与年龄相关的几何变化和 年龄内的可变性。(C)玻璃和硅橡胶的体外研究 模型将是复杂的脉冲复制器系统的组件 设计以匹配右侧的压力和流动特性 脑室。流动模式将使用激光光源进行可视化 用激光多谱勒风速计系统测量的速度和脉冲 多普勒装置类似于体内使用的装置。体外研究提供了 体内不具备灵活性；在以下情况下可以观察到流动模式 1)几何恒定和血流动力学可变的条件，2)恒定 血流动力学和可变几何，以及3)静息血流动力学和 几何形状，但不同的符合性。应统一所取得的成果 清楚地回答暗示的问题：1)这些几何图形是如何 右心室和主肺动脉从出生到成年的变化 生活？2)正常老化导致的几何变化是如何 和/或个体变异性会影响流动动力学吗？

The potential for measuring pulmonary blood velocity noninvasively with pulsed Doppler ultrasound has stimulated interest in relationships between velocity patterns and abnormal pulmonary hemodynamics. Unfortunately, clinical and experimental studies have found that characteristics reported in correlate well with abnormal pulmonary pressure and/or resistance are often observed in normal subjects. For example, the prominent backflow along the right posterior wall of the pulmonary trunk in patients with pulmonary hypertension, which has been attributed to enhanced curvature of the main pulmonary artery, has also been observed in normal lambs, dogs and humans. The similarity of animal velocity profiles in vivo to profiles obtained in pulsatile flow studies in curved tubes suggests that geometry plays a role as important as hemodynamics in determining velocity patterns. Thus, understanding the relationships 1) between normal maturation and geometry and 20 between geometry and fluid dynamics is essential if techniques for diagnosing altered fluid dynamics induced by congenital heart defects in infants and children, in whom pulmonary geometries will be changing rapidly, are to be improved. Using a series of developing lambs ranging from 1 day to 1 year in age, this study will address these issues by performing in vivo, in situ and in vitro experiments. (A) During the in vivo phase, velocity profiles will be obtained in the main and branch pulmonary arteries using 20 MHz pulsed Doppler devices. Data collected will be used to project normal -or-age 2- and 3-dimensional velocity profiles and input impedance spectra and to verify the authenticity of profiles determined in vitro in later studies. (B) Casts of the right ventricle and proximal pulmonary arteries will be made in situ under normal physiologic pressure. The casts, which reveal the importance of the subvalvar infundibular region, can be CT scanned and their structure committed to computer memory, from which 2- and 3-dimensional images can be reconstructed. Algorithms will be developed for quantifying curvature and torque of the main trunk, flow divider offset, bifurcation angles, taper, and segment dimensions. Data obtained will be used to quantitate age-related changes in geometry and intra-age variability. (C) In vitro studies in glass and silicone rubber models will be components of a sophisticated pulse duplicator system designed to match the pressure and flow characteristics of the right ventricle. Flow patterns will be visualized using a laser light source and velocity measured with a laser Doppler anemometer system and pulsed Doppler devices similar to those used in vivo. In vitro studies provide flexibility not available in vivo; flow patterns can be observed under conditions of 1) constant geometry and variable hemodynamics, 2) constant hemodynamics and variable geometry, and 3) resting hemodynamics and geometry but variable compliance. Unification of results obtained should answer clearly the questions implied: 1) how do the geometries of the right ventricle and major pulmonary arteries change from birth to adult life? and 2) how do geometric variations resulting from normal aging and/or individual variability affect flow dynamics?