Heterogenous Lung Model for Blunt Impact Loads Using Strain Rate-Dependent Material Properties of Parenchyma and Bronchi

This study aids in the development of a heterogeneous lung model for automobile crashes and blunt trauma. Existing finite element models of the lung tissue are modeled as homogeneous and consider only the parenchyma while ignoring the bronchi. Though the homogeneous model representation is computationally efficient, it cannot capture the true dynamics of the lung tissue. Therefore, in this study, dynamic compression tests were performed on porcine parenchyma at 1.6, 3, and 5 m/s. The maximum load increased from 23.4 to 55.6 N, with the average strain rate varying from 84 to 309 s-1. Strain rate-dependent bilinear material properties were estimated using a genetic algorithm-based inverse finite element (FE)-based optimization. These optimized bilinear parameters of parenchyma and porcine bronchi properties were used to develop an FE model of the heterogeneous lung sample. This heterogeneous model was then validated with test data obtained from dynamic compression tests on heterogeneous lung samples. Finally, a full-organ heterogeneous lung model was developed and studied for both frontal and side-impact scenarios. The side impact simulation revealed a rapid increase in maximum principal strain, ranging from 0.21 to 0.35 within 5.3 ms. In contrast, the homogeneous full-organ model exhibited a more gradual increase in strain, varying from around 0.23 to 0.35 over a span of 15.6 ms. Similarly, a significant difference was observed in the maximum strain rate between the homogeneous (207 s-1) and the heterogeneous models (352 s-1).