Modeling the effect of axial bronchial tension on expiratory flow.

Previous modeling of the expiratory flow-limiting mechanism is extended by including axial tension in the airway walls as one of the forces that affect airway mechanics. The analysis supports the Dawson-Elliott explanation of the plateaus in isovolume pressure-flow (IVPF) curves and shows that axial tension has the effect of increasing maximum flow and introducing a negative-effort-dependent region. Solutions for boundary conditions representing a cannula in the airways are qualitatively different with flow approaching zero as the pressure drop across the system becomes large.