FLUID–SOLID COUPLING STUDY OF AIRWAY TISSUE DEFORMATIONS UNDER AIRFLOW

The uvulopalatopharyngoplasty (UPPP) is a common surgical procedure used to treat obstructive sleep apnea (OSA). However, due to the unclear mechanism of action, it is not possible to achieve the ideal success rate for the surgery. The current studies mostly overlook the specific morphology of the patient’s upper airway or the elastic deformation of the airway soft tissues, which results in the existing results not being sufficient to effectively guide surgical treatment. In this study, we constructed an accurate three-dimensional upper airway model based on CT scan images of OSA patients before and after surgery, and simulated and studied the elastic deformations of soft tissues in the upper airway through bi-directional fluid-structure interaction (FSI) calculation. We compared the flow velocity, pressure distribution, and elastic deformation of the upper airways in successful and failed cases of surgery for OSA, and explained the cause of OSA and the mechanism of surgery from the perspective of fluid flow in the airway and deformation of the airway soft tissues. Our results showed that the size of the minimum cross-sectional area is not the decisive factor for the success of UPPP surgery. Successful surgery can reduce the negative pressure level on the airway walls and decrease the pressure drop between the inlet and outlet of the airway. In addition, by using the bi-directional FSI method, we further simplified a two-dimensional soft palate model to investigate the influence of the soft palate’s elastic modulus on the inhalation process. It is found that a softer palate can improve the flow field’s flow state when the elastic modulus of the soft palate is within the range of 0.5 MPa to 1.5 MPa, yet it is also more prone to deform and collapse. The fluid-solid coupling model developed in this study provides a research tool for personalized prediction of surgical outcomes.