Wilson T A, Hill M J, Hubmayr R D
Department of Aerospace Engineering and Mechanics, University of Minnesota, Minneapolis 55455, USA.
J Appl Physiol (1985). 1996 Apr;80(4):1144-8. doi: 10.1152/jappl.1996.80.4.1144.
Parenchymal markers were placed in the left caudal lobes of anesthetized dogs, and the three-dimensional positions of the markers were tracked by biplane videofluoroscopy during expiration from total lung capacity (TLC) to approximately 30% TLC at steady expiratory flows of 0.3-7% TLC/s. Regional volumes of samples of parenchyma with volumes at TLC of 1-5 cm3 were obtained by computing the volumes of tetrahedral defined by taking the markers, four at a time, as apices of the tetrahedra, Regional volume (Vr), as a fraction of volume at TLC, was plotted against average volume (VL), as a fraction of volume at TLC, and Vr was fit by a quadratic function of VL. The initial slopes of the plots, dVr/dVL at VL = 1, varied by +/- 26% from the mean slope of 1. The curvatures were highly correlated with the slopes, and the Vr vs. VL plots formed a nest of "onion skins". The initial slopes were weakly correlated with the vertical position of the centroid of the tetrahedron, with the slope increasing by approximately 20%/cm, on average, in the dorsal direction in the supine dog. The vertical gradient in Vr accounted for approximately 30% of the total variability; small-scale heterogeneity contributed the remaining 70%. These results confirm earlier quasistatic measurements of nonuniform Vr and provide the first data on curvature of Vr trajectories. The mechanisms that cause the nongravitational component of Vr variability and the curvatures of the trajectories are unknown.
在麻醉犬的左尾叶放置实质标记物，在从肺总量（TLC）稳定呼气至约30% TLC的过程中，通过双平面视频荧光镜检查追踪标记物的三维位置，呼气流量为0.3 - 7% TLC/秒。对于TLC时体积为1 - 5立方厘米的实质样本区域，通过计算以标记物为四面体顶点（每次取四个）所定义的四面体体积来获得区域体积。将区域体积（Vr）作为TLC时体积的分数，与平均体积（VL）作为TLC时体积的分数进行绘制，并且Vr由VL的二次函数拟合。在VL = 1时，图的初始斜率dVr/dVL与平均斜率1相差±26%。曲率与斜率高度相关，并且Vr与VL的图形成了一组“洋葱皮”。初始斜率与四面体质心的垂直位置弱相关，在仰卧位犬中，平均而言，斜率在背侧方向上每厘米增加约20%。Vr中的垂直梯度约占总变异性的30%；小尺度异质性贡献了其余的70%。这些结果证实了早期关于Vr不均匀性的准静态测量，并提供了关于Vr轨迹曲率的首批数据。导致Vr变异性的非重力分量和轨迹曲率的机制尚不清楚。
