Melsom M N, Kramer-Johansen J, Flatebø T, Müller C, Nicolaysen G
Department of Physiology, Institute of Basic Medical Sciences, University of Oslo, Norway.
Acta Physiol Scand. 1997 Mar;159(3):199-208. doi: 10.1046/j.1365-201X.1997.92355000.x.
Gravity has been regarded as the major determinant for local pulmonary perfusion and ventilation. Recent reports, describing major gravity independent heterogeneity in both variables, have questioned the importance of gravity. We asked to what extent ventilation and perfusion were related, and if they showed similar distributions along the vertical axis in the lung. We gave 99mTc-aerosols as tracers for ventilation and radioactive microspheres as blood flow tracers in five awake goats over 4 min. Ventilation and perfusion were determined in approximately 1.5 cm3 pieces of the lung. For both variables the vertical distribution could vary considerably from lung to lung, but within each lung the two distributions were similar. Both ventilation and perfusion were heterogeneously distributed (CV approximately 40% for both), they were highly correlated (r = 0.81) and the average 25-75-interpercentile interval for ventilation to perfusion ratio (0.84-1.13) was significantly less wide than for both ventilation (0.76-1.38) and perfusion (0.76-1.40). Some pieces were considerably overventilated while a few were correspondingly underventilated. This could indicate that perfusion is adjusted to ventilation in normoxic lungs with a low sensitivity to overventilation.
重力一直被视为局部肺灌注和通气的主要决定因素。最近的报告描述了这两个变量中存在主要的与重力无关的异质性，这对重力的重要性提出了质疑。我们研究了通气和灌注的相关程度，以及它们在肺的垂直轴上是否呈现相似的分布。我们在5只清醒的山羊身上，于4分钟内给予99mTc气溶胶作为通气示踪剂，放射性微球作为血流示踪剂。在肺的约1.5 cm³组织块中测定通气和灌注。对于这两个变量，垂直分布在不同肺之间可能有很大差异，但在每个肺内，这两种分布是相似的。通气和灌注均呈非均匀分布（两者的变异系数约为40%），它们高度相关（r = 0.81），通气/灌注比的平均25 - 75百分位数区间（0.84 - 1.13）明显比通气（0.76 - 1.38）和灌注（0.76 - 1.40）的区间窄。一些组织块通气过度，而一些则相应地通气不足。这可能表明在常氧肺中，灌注会根据通气进行调整，且对通气过度的敏感性较低。
