CARDIOPULMONARY GEOMETRY AND BLOOD FLOW IN GROWING LAMBS

无创测量肺血流速度的潜力 脉冲多普勒超声激发了人们对人际关系的兴趣 速度模式和异常肺血流动力学之间的关系。 不幸的是，临床和实验研究发现 报告的特征与肺异常密切相关 在正常受试者中经常观察到压力和/或阻力。对于 例如，沿着右后壁的明显回流 肺动脉高压患者的肺干 归因于主肺动脉曲率的增强，也 在正常的羔羊、狗和人类中观察到。动物的相似性 体内速度分布与脉动流研究中获得的分布 在弯曲的管子中表明几何形状起着与 确定速度模式的血流动力学。因此，了解 1) 正常成熟度与几何形状之间的关系以及 20 之间的关系 几何和流体动力学对于诊断技术至关重要 婴儿先天性心脏病引起的流体动力学改变 儿童的肺部几何结构将迅速发生变化， 得到改善。使用一系列发育中的羔羊，从 1 天到 1 天不等 岁，这项研究将通过在体内进行来解决这些问题， 原位和体外实验。 (A) 在体内阶段，速度 将使用以下方法获得主肺动脉和分支肺动脉的轮廓 20 MHz 脉冲多普勒设备。收集的数据将用于预测 正常或正常的 2 维和 3 维速度分布和输入阻抗 光谱并验证体外测定的剖面的真实性 后来的学习。 (B) 右心室和近端肺的铸型 动脉将在正常生理压力下原位制造。的 铸型揭示了瓣下漏斗区的重要性， 可以进行 CT 扫描，并将其结构保存到计算机内存中，从 可以重建 2 维和 3 维图像。算法将 开发用于量化主干线的曲率和扭矩、流量 分隔线偏移、分叉角度、锥度和段尺寸。数据 获得的结果将用于量化与年龄相关的几何变化和 年龄内的变异性。 (C) 玻璃和硅橡胶的体外研究 模型将成为复杂的脉冲复制器系统的组件 设计用于匹配正确的压力和流量特性 心室。使用激光光源将流动模式可视化 使用激光多普勒风速计系统和脉冲测量速度 多普勒装置与体内使用的装置类似。体外研究提供 体内不具备灵活性；可以观察到流动模式 1) 恒定几何形状和可变血流动力学条件，2) 恒定 血流动力学和可变几何形状，以及 3) 静息血流动力学和 几何形状但柔顺性可变。所获得的结果应统一 清楚地回答隐含的问题：1） 右心室和主要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产生的 和/或个体差异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?