We investigate the influence of bifurcation geometry, asymmetry of daughter airways, surfactant distribution and physicochemical properties on the uniformity of airway recruitment of asymmetric bifurcating airways. To do so, we developed micro-fluidic idealized in vitro models of bifurcating airways, through which we can independently evaluate the impact of carina location, and the daughter airway width and length. We explore the uniformity of recruitment and its relationship to the dynamic surface tension of the lining fluid, and relate this behavior to the hydraulic and capillary pressure drops (PHyd and PCap, respectively). These studies demonstrate the extraordinary importance of PCap in stabilizing reopening, even in highly asymmetric systems. The dynamic surface tension of pulmonary surfactant is integral to this stability because it modulates PCap in a velocity-dependent manner. Furthermore, the surfactant distribution at the propagating interface can have a very large influence on recruitment stability by focusing surfactant preferentially to specific daughter airways. This implies that modification of the surfactant distribution through novel modes of ventilation could be useful in inducing uniformly recruited lungs, aiding in gas exchange and reducing ventilator-induced lung injury (VILI).
- Copyright © 2016, Journal of Applied Physiology