Influence of bulk surfactant transport on airway reopening

During pulmonary airway reopening, a finger of air creates an interface that is continually expanding into a surfactant filled fluid. The quantity of surfactant transported to this interface affects the local surface tension, γ, and thus the reopening pressure. The goal of this study is to demonstrate how transport barriers can affect the mechanics of this system. We use a combined boundary integral and finite difference technique to solve the governing equations in an axisymmetric geometry. When the quantity of surfactant in the fluid is low, a bulk diffusion barrier exists such that C_s<C₀ , where C_s is the concentration near the interface and C₀ is the upstream concentration. Under these conditions, reopening pressures are elevated since γ>γ_eq, the equilibrium surface tension