Construction of a computational mechanical model of bronchi for practical simulation of the optimal positive intrathoracic pressure conditions during general thoracic surgery.

BACKGROUND Thoracic CO2 insufflation with positive intrathoracic pressure is usually effective during thoracoscopic surgery, however, lung collapse is sometimes insufficient. We hypothesized that inappropriate bronchial collapse might cause this unsuccessful lung collapse. OBJECTIVE The objective of this study was to construct a computational mechanical model of bronchi for practical simulation to discover the optimal conditions of positive intrathoracic pressure during thoracoscopic surgery. METHODS Micro-focus high-resolution X-ray computed tomography measurements of lungs from just-slaughtered swine were extracted, and the three-dimensional geometries of the bronchi under pressurized and depressurized conditions were measured accurately. The mechanical properties of the bronchus were also measured. Computational fluid dynamics (CFD) and computational structural mechanics (CSM) analyses were conducted. RESULTS The CSM results indicated that the present structural model could simulate bronchial occlusion. The CFD results showed that airflows from pressed lung alveoli might cause low-internal-pressure regions when suddenly or heterogeneously pushed airflow was injected from a small branching bronchus to a large bronchus. A preliminary computational mechanical model of bronchi was constructed. CONCLUSIONS We demonstrated the performance of the mechanical model of bronchi in rough simulations of bronchial occlusions. However, this model should be verified further using human data to facilitate its introduction to clinical use.