Finite element analysis of the mechanical behavior of preterm lamb tracheal bifurcation during total liquid ventilation

Knowledge of the mechanical behavior of immature airways is crucial to understand the effects exerted by ventilation treatments, namely by Total Liquid Ventilation (TLV). A computational approach was adopted to investigate preterm airways in the range of pressure applied during TLV. A 3D finite-element model of the tracheal bifurcation was developed. Structural analyses were performed using ABAQUS/Standard to evaluate airway deformation during TLV. The model consists of 7 rings, each composed of 3 tissues (cartilage, smooth muscle, connective tissue) modeled as hyperelastic materials. Biomechanical experimental tests were performed on lamb tracheae to obtain the stress-strain relationship for each tissue. Pressure load was applied on the internal surface of the model, reproducing the airway pressure tracing acquired during a TLV breath ending with a tracheal collapse phenomenon. Model reliability was verified by comparing the model outcomes to computer tomography scan images acquired during animal TLV trials. The simulations show progressive lumen narrowing during expiration, at increasing negative pressure until the occurrence of collapse; however not inducing complete airway occlusion. A reliable model was obtained to help setting ventilation parameters during TLV.