A morphometric lung model for evaluating lung aeration at birth

Background: Lung aeration must rapidly develop at birth, but how to promote it without injuring the fragile lung is still unknown. Mathematical models simulating lung mechanics during this transition may help understand the underlying physiological mechanisms and design protective ventilation strategies. This study develops a morphologically-coherent computational lung model incorporating changing physical conditions during the transition from liquid-filled to gas-filled lungs. Methods: We adapted a 3-D morphological model of the adult airway tree adjusting airway dimensions, lung volume, and lung tissue mechanical properties. Changes in resistance, inertia, and compliance during aeration were modeled by considering the differing properties of fetal fluid versus air. The capillary pressure at the liquid-air interface was computed using Laplace equation. Terminal airway diameters increased with lung volume due to airway-parenchymal interdependence. An integrated circuit simulator solved the entire network in the time domain. Results: The air volume entering the model at different applied pressures increased exponentially with time. With 30 cmH2O applied, lung volume reached total capacity after 15 s, matching lung aeration dynamics observed in animal models and human infants. In contrast, after the same time, at 15 cmH2O, lung volume was slightly above functional residual capacity, and at 10 cmH2O, it remained below. Conclusions: The proposed in-silico newborn lung model simulates lung aeration at birth, allowing observation of the airway emptying sequence and the heterogeneity of aeration at each time point. Integrating this model with comprehensive acinar models may aid in defining protective resuscitation ventilation strategies for recruiting the lung minimizing risk of injuries.