Modeling lung tissue dynamics and injury under pressure and impact loading

Area of Science:

• Biomechanics
• Computational Biology
• Medical Engineering

Background:

• Understanding lung mechanics under high-rate loading is crucial for injury assessment.
• Existing models may not fully capture complex viscoelastic and damage behaviors.

Purpose of the Study:

• To implement and evaluate a nonlinear viscoelastic lung model for high-rate loading scenarios.
• To incorporate a damage-injury component based on internal energy and its gradients.

Main Methods:

• Developed a nonlinear viscoelastic model with closed-cell compressibility and a damage-injury mechanism.
• Adapted the model for explicit finite element simulations using strain energy density rate and wave speed.
• Validated predictions against experimental data for direct pressure pulse loading and projectile impacts on extracted lung tissue.

Main Results:

• Model predictions for pressure pulse loading showed good agreement with experimental observations, including an injury threshold correlating with edema.
• Simulations of projectile impacts demonstrated comparable penetration depths and a strong correlation between impact velocity and damage severity.
• Damage initiation and propagation patterns from the impact surface aligned with empirical evidence, though predicted injury severity exceeded experimental findings for surface loading.

Conclusions:

• The nonlinear viscoelastic lung model shows promise for simulating high-rate loading and predicting lung injury.
• The model successfully captures key aspects of lung response, including pressure thresholds and impact dynamics.
• Discrepancies in predicted injury severity warrant further model refinement and analysis.