The importance of nasal airflow distribution for olfactory function and paranasal sinus ventilation: insights from a computational fluid dynamics evaluation in dupilumab‐treated CRSwNP patients

Background: Dupilumab is an established treatment for severe chronic rhinosinusitis with nasal polyps (CRSwNP), leading to significant improvements in symptoms and olfactory function. However, objective data on how dupilumab modifies nasal airflow distribution and paranasal sinus ventilation are limited. Computational fluid dynamics (CFD) allows detailed, quantitative evaluation of nasal airflow changes that cannot be assessed in vivo. This study aims to quantify changes in nasal airflow, olfactory cleft ventilation, and paranasal sinus patency after dupilumab treatment, and to explore their relationship with olfactory outcomes. Methods: This retrospective, single-center CFD study included 26 adult patients with type 2 CRSwNP treated with dupilumab for 6 months. Paired pre- and post-treatment CT scans (52 scans) were analyzed using registered CFD simulations. Total nasal airflow and airflow distribution across three nasal sections were quantified during inspiration and expiration. Olfactory function was assessed using the Sniffin’ Sticks Identification Test (SSIT-16). Paranasal sinus patency was scored (0–16) and correlated with the Completion of Surgery Index (CoSI). Pre- and post-treatment differences were analyzed using Wilcoxon signed-rank tests and correlations with Spearman’s rho. Results: After 6 months, total inspiratory airflow increased from 17.35 ± 6.70 to 22.30 ± 4.71 L/min ( p = 0.003), while total expiratory airflow increased from 18.15 ± 6.51 to 21.86 ± 5.69 L/min ( p = 0.025). The greatest relative airflow increase occurred in the olfactory cleft ( + 567% inspiratory). SSIT-16 scores increased from 4.7 ± 3.2 to 10.3 ± 2.7, and the change in inspiratory airflow within the olfactory section significantly correlated with the change in SSIT-16 score ( ρ= 0.431, p = 0.028). Paranasal sinus patency increased by 7.5 points ( p < 0.01), without a significant correlation with CoSI. Conclusions: Dupilumab significantly improves nasal airflow and paranasal sinus ventilation in CRSwNP. Increased airflow in the olfactory cleft is associated with improved olfactory function, supporting a conductive component of smell loss in these patients.