Authors
   Adler A. Bates JH.
Institution
   Department of Biomedical Engineering, McGill University, Montreal, Quebec,
   Canada.
Title
   A micromechanical model of airway-parenchymal interdependence.
Source
   Annals of Biomedical Engineering. 28(3):309-17, 2000 Mar.
Abstract
   The forces of parenchymal interdependence in the lung are potent
   inhibitors of airway smooth muscle shortening, as evidenced by the marked
   dependence of bronchial responsiveness on lung volume. In this study we
   developed a mathematical-computer model of the effects of parenchymal
   interdependence on airway smooth muscle shortening. A three-dimensional
   network of cuboidal alveolar walls was tethered at its boundaries and
   surrounded a single airway with mechanical properties identical to the
   alveolar parenchyma. The walls were assigned highly nonlinear properties
   so that the pressure-volume behavior of the model matched that measured in
   dogs. Constriction of the airway was achieved by increasing the
   circumferential tension in the airway wall, and then solving the
   force-balance equations of the model to calculate the equilibrium
   configurations of the airway wall and all the interconnecting alveolar
   walls. The changes in airway resistance predicted by the model at various
   transpulmonary pressures (P(tp)) were compared to those obtained by the
   alveolar capsule oscillator technique in dogs during induced
   bronchoconstriction at various P(tp) (Balassy et al., J. Appl. Physiol.
   78:875-880, 1995). The model matched the data reasonably well at P(tp)
   values above about 0.5 kPa, but was too responsive at lower P(tp). We were
   able to make the model match the data at all P(tp) by including an
   additional stiffness term, such as might conceivably arise from the airway
   wall itself.