조직 물성치가 다른 연결 폐포사이의 비동시성 호흡 특성

Abstract

The dynamic characteristics of pressure-volume (P-V) curves and asyn-chronous ventilation were explored for two populations of alveoli or acini with dissimilar mechanical properties or geometric dimensions that communicate with each other in a branching structure. The equations for the dynamic change of pres-sure and volume during a respiration cycle in either alveolar or acinar populations were formulated using the Poiseuille and Laplace equations, respectively. Surface tension of the air-liquid interface on the surface of the alveolar walls and tissue viscoelasticity from collagen and elastin fibers were the main forces determining the dynamics of respiration. The dynamic surfactant model of Otis et al. was used to describe surface tension and the quasi-linear viscoelastic (QLV) theory of Fung was used to describe tissue viscoelastic forces.The P-V characteristics obtained in this model and the dynamic properties of the model alveoli calculated from the results are qualitatively in good agreement with experimental observations. The model suggests that any asymmetric alveolar condition causes asynchronous breathing and the degree of asynchrony increases in proportion with the level of asymmetry in alveolar conditions. Also, the degree of asynchrony depends more strongly on differences in tissue viscoelastic proper-ties or in diameter of branches connecting the alveoli than on surface tensile prop-erties or length asymmetry. The modeled level of asynchrony increased with de-creasing breathing frequency, but was relatively insensitive to tidal volume. Moreover, the P-V characteristics of normal acini in communication with abnormal acini were changed substantially by the presence of abnormal one.