Mechanical stress in a solid ellipsoid model of the lung after thoracoscopic surgery for spontaneous pneumothorax.

Background: Newly formed bullae after video-assisted thoracoscopic surgery (VATS) bullectomy in primary spontaneous pneumothorax (PSP) are an important etiology for recurrence and are associated with mechanical stress along the stapling line. However, the distribution or pattern of stress after VATS bullectomy has not been thoroughly investigated. Our aim was to analyze the stress distribution following lung resection.

Methods: Using finite element method analyses in COMSOL Multiphysics software to evaluate the stress distribution along the stapling line, a solid ellipsoidal lung model was constructed. Simulations were subsequently conducted to evaluate changes in stress along the stapling line after VATS bullectomy. Finally, a parametric study investigating the changes in stress based on the difference between the lung resection volume and the degree of lung collapse was conducted.

Results: The magnitude of the stress progressively increased with the inflation of the lung, and the highest stresses were observed at both ends and the center of the stapling line. The parametric studies showed that the maximum stress observed was positively correlated with the amount of lung resection (R=0.961, P<0.001) and negatively correlated with the degree of lung collapse before stapling (R=0.964, P<0.001). A wrinkling phenomenon was also observed adjacent to the stapling line.

Conclusions: The mechanical stress during inflation progressively increased, reaching its peak at both ends and in the center, resulting in uneven wrinkling along the stapling line. Minimal resection with incomplete collapse before stapling could be considered a potential strategy to reduce stress.