Clough A V, Haworth S T, Hanger C C, Wang J, Roerig D L, Linehan J H, Dawson C A
Department of Mathematics, Statistics and Computer Science, Marquette University, Milwaukee, WI 53201-1881, USA.
J Appl Physiol (1985). 1998 Aug;85(2):565-74. doi: 10.1152/jappl.1998.85.2.565.
Knowledge of the contributions of arterial and venous transit time dispersion to the pulmonary vascular transit time distribution is important for understanding lung function and for interpreting various kinds of data containing information about pulmonary function. Thus, to determine the dispersion of blood transit times occurring within the pulmonary arterial and venous trees, images of a bolus of contrast medium passing through the vasculature of pump-perfused dog lung lobes were acquired by using an X-ray microfocal angiography system. Time-absorbance curves from the lobar artery and vein and from selected locations within the intrapulmonary arterial tree were measured from the images. Overall dispersion within the lung lobe was determined from the difference in the first and second moments (mean transit time and variance, respectively) of the inlet arterial and outlet venous time-absorbance curves. Moments at selected locations within the arterial tree were also calculated and compared with those of the lobar artery curve. Transit times for the arterial pathways upstream from the smallest measured arteries (200-micron diameter) were less than approximately 20% of the total lung lobe mean transit time. Transit time variance among these arterial pathways (interpathway dispersion) was less than approximately 5% of the total variance imparted on the bolus as it passed through the lung lobe. On average, the dispersion that occurred along a given pathway (intrapathway dispersion) was negligible. Similar results were obtained for the venous tree. Taken together, the results suggest that most of the variation in transit time in the intrapulmonary vasculature occurs within the pulmonary capillary bed rather than in conducting arteries or veins.
了解动脉和静脉传输时间离散对肺血管传输时间分布的影响，对于理解肺功能以及解释包含肺功能信息的各类数据非常重要。因此，为了确定肺动脉和静脉树内血液传输时间的离散情况，使用X射线微焦点血管造影系统获取了通过泵灌注犬肺叶血管系统的造影剂团注图像。从这些图像中测量叶动脉、叶静脉以及肺内动脉树内选定位置的时间-吸光度曲线。肺叶内的总体离散度由入口动脉和出口静脉时间-吸光度曲线的一阶矩和二阶矩（分别为平均传输时间和方差）之差确定。还计算了动脉树内选定位置的矩，并与叶动脉曲线的矩进行比较。测量的最小动脉（直径200微米）上游动脉路径的传输时间不到肺叶总平均传输时间的约20%。这些动脉路径之间的传输时间方差（路径间离散度）不到造影剂团注通过肺叶时总方差的约5%。平均而言，沿给定路径发生的离散度（路径内离散度）可忽略不计。静脉树也得到了类似结果。综合来看，结果表明肺内血管系统中传输时间的大部分变化发生在肺毛细血管床内，而非传导动脉或静脉中。
