Lucas C L, Henry G W, Ferreiro J I, Ha B, Keagy B A, Wilcox B R
Department of Surgery, University of North Carolina, Chapel Hill 27599.
Heart Vessels. 1988;4(2):65-78. doi: 10.1007/BF02058992.
Clinical investigations focused on finding characteristics of noninvasively obtained measurements of pulmonary blood velocity that can be used to quantitate pulmonary blood flow and/or pulmonary pressure have often yielded results whose imprecision has been attributed to flow pattern variability. To determine flow pattern variability in an in vivo animal model in varying hemodynamic states, main pulmonary artery blood velocity waveforms were recorded in 17 dogs at 2-mm intervals along an anterior to posterior wall-oriented axis using a 20-MHz pulsed Doppler needle probe. Control data were obtained before the animals were subjected to altered flow (atrial level shunts) and pressure (10% O2 inhalation) states. Instantaneous velocity profiles were computed throughout the cardiac cycle. Estimates of pulmonary blood flow were obtained assuming an elliptical model of the pulmonary artery which allowed computation of velocity at all points in the cross section, based on the measured values along the axis. Model-based estimates were compared to measured values and estimates obtained in the traditional fashion, i.e., the product of centerline velocity and cross-sectional area. Results clearly showed marked interanimal variability, even in control states. Reverse flow in the posterior half of the vessel, which tended to become more pronounced with increased pulmonary artery pressure, was observed during late systole and early diastole. Elevated pulmonary blood flow tended to increase the maximum velocities along the anterior wall relative to midline velocities. Neither estimate of cardiac output yielded consistently accurate results (r = 0.77 for model-based method, r = 0.80 for area times central velocity method). Findings of this study, which highlight the dependency of waveform characteristics on sampling site, the large degree of intersubject variability, and the need for large or multiple sample volumes for pulmonary blood flow determination, help clarify inconsistencies observed by clinicians and suggest that future work with animal models will facilitate a greater understanding of the determinants of human pulmonary velocity waveforms.
临床研究聚焦于寻找可用于定量肺血流量和/或肺压力的无创性肺血流速度测量的特征，但其结果往往不够精确，这归因于血流模式的变异性。为了确定在不同血流动力学状态下的体内动物模型中的血流模式变异性，使用20MHz脉冲多普勒针式探头，沿着从前壁到后壁的轴向，以2毫米的间隔记录了17只狗的主肺动脉血流速度波形。在动物处于改变的血流（心房水平分流）和压力（吸入10%氧气）状态之前获取对照数据。计算整个心动周期的瞬时速度剖面。假设肺动脉为椭圆形模型，根据轴向上的测量值计算横截面上所有点的速度，从而获得肺血流量的估计值。将基于模型的估计值与测量值以及以传统方式获得的估计值（即中心线速度与横截面积的乘积）进行比较。结果清楚地表明，即使在对照状态下，动物之间也存在明显的变异性。在收缩期末期和舒张早期观察到血管后半段出现逆流，随着肺动脉压力升高，逆流往往变得更加明显。肺血流量增加往往会使前壁的最大速度相对于中线速度增加。两种心输出量估计方法均未产生始终准确的结果（基于模型的方法r = 0.77，面积乘以中心速度法r = 0.80）。本研究的结果突出了波形特征对采样部位的依赖性、受试者间的高度变异性以及确定肺血流量需要大样本量或多个样本量，有助于澄清临床医生观察到的不一致性，并表明未来对动物模型的研究将有助于更深入地理解人类肺血流速度波形的决定因素。
