Evaluation of Septoplasty on Airflow Patterns in A Patient with Nasal Septal Deviation Using Computational Fluid Dynamics

Background: The fluid flow in channels with deviation change in the cross-sectional area in a part of the channel can have a turbulent behavior. Nasal Septal Deviation (NSD) is such channel and can disturb airflow. Computational Fluid Dynamics (CFD) can show the critical points that cause turbulence or blockage of the flow by analyzing the airflow passing through the nasal cavity in detail. Objective: We evaluated a patient with nasal septal deviation before and after correcting septum surgery (septoplasty). With the help of Computational Fluid Dynamics (CFD) by showing the patterns of airflow through the patient's nasal cavity and accurately locating the deviation of the septum along with showing the disturbance of the passing airflow to the surgeon, it is possible to preserve healthy tissues. Methods: First, Computed Tomography (CT) of the nasal cavity and paranasal sinuses was done. Then, using Mimics software, the basic 3D geometry of the nose was made. Due to the point-like nature of the created shape, we converted the 3D geometry from the point to a linear geometry and finally to a volumetric geometry by CATIA software. Considering the transient flow from the nasal tip, simulation of the numerical method at air flow rates of 15, 17.4, 20, 25 and 40 lit/min was done using the k-ω SST turbulence model. We considered the non-slip and smooth nasal wall and steady flow at 22 ᵒC. According to CFD data and turbulence area the exact location of nasal cavity which caused obstruction was shown to surgeon and septoplasty was done. 3D modeling using CFD was done and airflow parameters were evaluated again three months after surgery to evaluate development of airflow behavior. Results: The peak velocity was found at 3 to 6 cm from the nostril before septoplasty, but the peak velocity was at the nasal valve after septoplasty. The airflow resistance decreased from 0.97 Pa×min/lit to 0.53 Pa×min/lit after septoplasty for a flow rate of 17.4 lit/min (the beginning of airflow disturbance). Also, the pressure drop for a flow rate of 17.4 liters per minute was 16.878 Pa, which decreased to 9.222 Pa after surgery. The highest wall shear stress was also at a distance of 4.1 and 5.07cm from nasal tip before and after septoplasty respectively. The highest wall shear stress was 3.85×10-2 Pa before septoplasty, but after septoplasty it decreased to 2.78×10-2 Pa. Conclusion: Nasal septal deviation increases the velocity, resistance, pressure drop and creates a vortex in the airflow, which leads to obstruction of the airway passing through the nasal cavity. CFD showed difference in nasal airflow parameters in patients with deviated nasal septum before and after septoplasty, so it can help surgeon find the exact area which causes obstruction and septoplasty can be done according to CFD data.