Expiratory flow from a non-homogeneous human lung model

The merging of two dissimilar flows in a tube junction is underspecified by the conservation laws for mass and energy. An empirical result provides the required extra equation, which, together with an existing model for a homogeneous lung, has enabled the development of a model for expiratory flow from a nonhomogeneous lung. The model has been used to investigate both maximal and partial forced expirations as well as steady submaximal flows. The investigations were carried out with asymmetric peripheral airway constrictions with both central and more peripheral mixing of the flows. The alveolar pressure differences which developed showed a rapid initial rise followed by a plateau region before declining to zero at end-expiration. For flows merged in lobar bronchi, serial choke points were found over much of the midvital capacity. Moderately severe unilateral peripheral constriction gave rise to a significant elevation of maximal flow when the expiration started at 50% VC and flows were merged peripherally.<>