Computational fluid dynamics analysis of nasal airway in patients with unilateral cleft lip nasal deformity: a pilot...

Patients with unilateral cleft lip nasal deformity (CLND) frequently suffer from nasal airway obstruction, but the precise location of increased resistance remains unclear. This pilot study aimed to investigate the fluid dynamic characteristics of the nasal airway in patients with unilateral CLND using computational fluid dynamics (CFD). Seven patients with unilateral complete CLND who had undergone preoperative cranial computed tomography (CT) were randomly selected. Three-dimensional (3D) upper airway models were reconstructed from CT data, and steady-state simulations were performed using the standard k-ω turbulence model with an inlet flow rate of 400 mL/s. Airflow velocity and pressure at the internal nasal valve (INV), external nasal valve (ENV), and the most deviated portion of the nasal septum were compared between the cleft and non-cleft sides during inspiration and expiration. During inspiration, the mean airflow velocity at the ENV on the cleft side was significantly lower than on the non-cleft side (4.27 ± 1.22 vs 5.71 ± 0.79 m/s; p = 0.022), whereas no significant differences were observed at the INV or nasal septum during inspiration, nor at any site during expiration. Pressure values showed no significant differences between sides at any phase. Pressure contour and velocity vector maps visually confirmed that the greatest pressure drop and flow disturbance occurred in the nasal vestibule/ENV region. In conclusion, this pilot CFD analysis suggests that airflow disturbance in unilateral CLND is mainly localized to the ENV/nasal vestibule region rather than the INV or the deviated septum. These findings should be interpreted as preliminary and hypothesis-generating, and may help guide future studies evaluating whether surgical restoration of lower lateral cartilage position improves nasal airway function.