Nixon W, Pack A I
J Appl Physiol Respir Environ Exerc Physiol. 1982 Aug;53(2):496-504. doi: 10.1152/jappl.1982.53.2.496.
There is debate over the mechanisms that produce the alveolar slope, with theories relating to both series and parallel inhomogeneity being proposed. We use a mathematical model of pulmonary gas transport, which incorporates both series and parallel effects, to investigate the relevance of each in the production of this alveolar slope. Interaction between lung units is specifically studied by simulating mixing at both proximal- and distal-branch points in the bronchial tree. During expiration mixing of the gas from inhomogeneous parallel lung units leads to concentration gradients within each unit. The resultant effect on the concentration of the expirate depends on the position in the bronchial tree at which this mixing takes place; proximal interaction alters the initial phase of the expired concentration profile, whereas distal interaction changes the magnitude of the alveolar slope. The net effect of distal interaction is to produce a greater alveolar slope for gases with low molecular diffusivity. These effects are present even in the absence of asynchronous emptying of lung units but may be enhanced by it. These results help to clarify controversies about the mechanisms underlying production of the alveolar slope.
关于产生肺泡斜率的机制存在争议，有人提出了与串联和并联不均匀性相关的理论。我们使用一个肺气体传输的数学模型，该模型纳入了串联和并联效应，以研究它们各自在产生这种肺泡斜率中的相关性。通过模拟支气管树近端和远端分支点的混合，专门研究了肺单位之间的相互作用。在呼气过程中，来自不均匀并联肺单位的气体混合会导致每个单位内出现浓度梯度。对呼出气体浓度的最终影响取决于这种混合在支气管树中发生的位置；近端相互作用改变呼出浓度曲线的初始阶段，而远端相互作用则改变肺泡斜率的大小。远端相互作用的净效应是使分子扩散率低的气体产生更大的肺泡斜率。即使在肺单位不存在异步排空的情况下，这些效应也存在，但可能会因异步排空而增强。这些结果有助于澄清关于肺泡斜率产生机制的争议。
