Schwardt J D, Gobran S R, Neufeld G R, Aukburg S J, Scherer P W
Department of Bioengineering, School of Engineering and Applied Science, University of Pennsylvania, Philadelphia 19104.
Ann Biomed Eng. 1991;19(6):679-97. doi: 10.1007/BF02368076.
A numerical solution of the convection-diffusion equation with an alveolar source term in a single-path model (SPM) of the lung airways simulates steady state CO2 washout. The SPM is used to examine the effects of independent changes in physiologic and acinar structure parameters on the slope and height of Phase III of the single-breath CO2 washout curve. The parameters investigated include tidal volume, breathing frequency, total cardiac output, pulmonary arterial CO2 tension, functional residual capacity, pulmonary bloodflow distribution, alveolar volume, total acinar airway cross sectional area, and gas-phase molecular diffusivity. Reduced tidal volume causes significant steepening of Phase III, which agrees well with experimental data. Simulations with a fixed frequency and tidal volume show that changes in blood-flow distribution, model airway cross section, and gas diffusivity strongly affect the slope of Phase III while changes in cardiac output and in pulmonary arterial CO2 tension strongly affect the height of Phase III. The paper also discusses differing explanations for the slope of Phase III, including sequential emptying, stratified inhomogeneity, and the issue of asymmetry, in the context of the SPM.
在肺气道单路径模型（SPM）中，带有肺泡源项的对流扩散方程的数值解模拟了稳态二氧化碳清除过程。该单路径模型用于研究生理参数和腺泡结构参数的独立变化对单次呼吸二氧化碳清除曲线第三阶段斜率和高度的影响。所研究的参数包括潮气量、呼吸频率、心输出量、肺动脉二氧化碳张力、功能残气量、肺血流分布、肺泡体积、腺泡气道总横截面积和气态分子扩散率。潮气量减少会导致第三阶段显著变陡，这与实验数据非常吻合。在固定频率和潮气量的模拟中表明，血流分布、模型气道横截面积和气体扩散率的变化强烈影响第三阶段的斜率，而心输出量和肺动脉二氧化碳张力的变化强烈影响第三阶段的高度。本文还在单路径模型的背景下讨论了对第三阶段斜率的不同解释，包括顺序排空、分层不均匀性和不对称问题。
