Glenny R W
Department of Medicine, University of Washington, Seattle 98196.
J Appl Physiol (1985). 1992 Jun;72(6):2378-86. doi: 10.1152/jappl.1992.72.6.2378.
Despite the heterogeneous distribution of pulmonary blood flow, perfusion appears to be spatially ordered, with neighboring regions of lung having similar magnitudes of flow. This premise was tested by determining the spatial correlation of regional flow [rho(d)] as a function of distance (d) between regions. Regional pulmonary perfusion was measured in both supine and prone positions in seven anesthetized mechanically ventilated dogs with radiolabeled microspheres. After excision and drying, the lungs were cubed into pieces 1.2 cm on a side, with a three-dimensional coordinate assigned to each piece. The microsphere-determined flow to each piece was measured by radioactive counts, and rho(d) was calculated for all paired pieces within the same lobe. rho(d) was greatest for adjacent pieces (d = 1.2 cm) and decreased with increasing d, becoming negative at large distances in all dogs and positions. The spatial correlation of flow between adjacent pieces, rho(1.2 cm), was greater in the supine than in the prone position (0.66 vs. 0.72, P less than 0.05). The observations for each dog and position were fit to the equation rho(d) = d(a)+b.d+c, and the coefficients were used to compare rho(d) in the supine and prone positions. rho(d) differed in the two positions (P less than 0.05), with rho(d) falling off more rapidly with distance in the supine position. When trends in flow due to gravity were mathematically removed, differences between supine and prone positions were no longer observed. The spatial correlation of regional pulmonary perfusion was anisotropic in both supine and prone positions. The observation that regional pulmonary perfusion is highly correlated over large spatial distances has important implications for models of flow distribution.
尽管肺血流分布不均，但灌注在空间上似乎是有序的，相邻肺区域的血流大小相似。通过确定区域血流的空间相关性[rho(d)]作为区域间距离(d)的函数来验证这一前提。在7只麻醉状态下机械通气的狗中，使用放射性微球测量了仰卧位和俯卧位的区域肺灌注。切除并干燥后，将肺切成边长为1.2 cm的小块，每块赋予一个三维坐标。通过放射性计数测量每个小块的微球测定血流，并计算同一叶内所有配对小块的rho(d)。相邻小块(d = 1.2 cm)的rho(d)最大，并随d的增加而减小，在所有狗和体位的远距离处变为负值。相邻小块间血流的空间相关性rho(1.2 cm)，仰卧位大于俯卧位(0.66对0.72，P<0.05)。将每只狗和体位的观察结果拟合到方程rho(d)=d(a)+b.d+c，并使用这些系数比较仰卧位和俯卧位的rho(d)。两个体位的rho(d)不同(P<0.05)，仰卧位时rho(d)随距离下降得更快。当通过数学方法消除重力引起的血流趋势时，仰卧位和俯卧位之间的差异不再明显。仰卧位和俯卧位时区域肺灌注的空间相关性均为各向异性。区域肺灌注在大空间距离上高度相关这一观察结果对血流分布模型具有重要意义。
