Effect of lung inflation and airway muscle tone on airway diameter in vivo
Effect of lung inflation and airway muscle tone on airway diameter in vivo
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DOI：
10.1152/jappl.1996.80.5.1581
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发表时间：
1996-05-01
影响因子：
3.3
通讯作者：
Mitzner, W
中科院分区：
文献类型：
--
作者：
Brown, RH;Mitzner, W
正常气道尺寸如何随肺容量变化对于确定正常用力肺活量操作期间的流量限制以及阻塞性肺疾病的表现非常重要。文献呈现出一幅令人困惑的画面，一些结果表明气道直径随肺容量的立方根线性增加，而另一些结果则显示出高度非线性关系。平滑肌收缩对肺气道相互依赖性的影响甚至还不太清楚。最近的形态学工作明确假设气道基底膜是不可扩张的，尽管达到最大气道尺寸时的肺容量尚不清楚。随着平滑肌收缩，上皮和基底膜的折叠导致管腔面积的变化。在这项研究中，我们通过在不同跨肺压下使用高分辨率计算机断层扫描（每次保持 2 分钟）来测量肺充气对放松和收缩气道区域的影响。我们发现，完全放松的气道在压力达到 5-7 cmH(2)O (P < 0.001) 时相当可扩张，在气道压力达到 30 cmH(2)O (P = 0.49) 时气道达到最大尺寸，不再进一步扩张。因此，松弛的气道显然不会随着肺部各向同性地扩张。对于平滑肌张力，不同动物的气道对肺膨胀的反应不同，一些动物在气道压力为 20 cmH(2)O 时表现出最小的气道扩张，而另一些动物则表现出更容易随着肺扩张而扩张的气道。然而，即使气道压力高达 30 cmH(2)O，这些适度收缩的气道通常也无法达到最大直径。因此，体内短暂的深吸气预计只会对收缩的气道产生很小的影响。
How normal airway dimensions change with lung volume is of great impor tance in determining flow limitation during the normal forced vital capacity maneuver as well as in the manifestation of obstructive lung disease. The literature presents a confusing picture, with some results suggesting that airway diameter increases linearly with the cube root of lung volume and others showing a highly nonlinear relation. The effect of smooth muscle contraction on lung-airway interdependence is even less well understood. Recent morphological work explicitly assumes that airway basement membrane is nondistensible, although the lung volume at which this maximal airway size is reached is unknown. With smooth muscle contraction, folding of the epithelium and basement membrane accounts for the changes in luminal area. In this study, we measured the effect of lung inflation on relaxed and contracted airway areas by using high-resolution computed tomography at different transpulmonary pressures, each held for 2 min. We found that fully relaxed airways are quite distensible up to a pressure of 5-7 cmH(2)O (P < 0.001), where they reach a maximal size with no further distension up to an airway pressure of 30 cmH(2)O (P = 0.49). Thus relaxed airways clearly do not expand isotropically with the lung. With smooth muscle tone, the airways in different animals responded differently to lung inflation, with some animals showing minimal airway dilation up to an airway pressure of 20 cmH(2)O and others showing airways that were more easily dilated with lung expansion. However, maximal diameter of these moderately constricted airways was not usually achieved even up to an airway pressure of 30 cmH(2)O. Thus a transient deep inspiration in vivo would be expected to have only a small effect on contracted airways.