Investigating the Pathogenesis of Eosinophilic Chronic Rhinosinusitis (ECRS): Insights from a CFD Study of Nasal Airflow

ECRS involves chronic inflammation, but the fluid dynamic factors contributing to its pathogenesis and recurrence remain poorly understood. Nasal polyps in ECRS often develop in poorly ventilated regions (uncinate process, middle turbinate, ethmoid infundibulum), suggesting a link between local airflow and disease development. While nasal airflow has been analyzed using computational fluid dynamics (CFD) in previous studies, fluid dynamic factors potentially contributing to local inflammation and its recurrence have not been sufficiently explored.

We reconstructed a patient-specific nasal cavity from postoperative CT scans obtained prior to recurrence in an ECRS patient, and performed unsteady CFD simulations of nasal airflow. Simulations were conducted using a tetrahedral mesh under laminar flow conditions. To replicate natural breathing, a sinusoidal inlet flow was applied over two cycles (exhalation: 3–5 s; inhalation: 5–7 s). Forward volume flow rate (FVF) and average pressure (AP) in both frontal sinuses was evaluated during inhalation and exhalation.

Postoperative recurrence occurred mainly in the ethmoid sinus, middle meatus, and frontal sinus, with the right frontal sinus being the most severely affected. FVF results revealed asymmetric ventilation between the frontal sinuses. During inhalation, flow into the right frontal sinus (4.21 mL/s) slightly exceeded that of the left (3.75 mL/s), whereas during exhalation, flow out of the left (12.9 mL/s) far exceeded that from the right (2.52 mL/s). Overall, the left frontal sinus had roughly double the total volume exchange. This indicates that the left frontal sinus was well ventilated, whereas poor ventilation on the right may have contributed to the observed recurrence. Additionally, previous studies have shown that mechanical pressure on nasal polyp–derived epithelial cells can promote the expression of inflammation-related genes. In our case, the AP in the right frontal sinus was approximately 5 Pa higher than in the left, which may stimulate the sinus mucosa and contribute to local inflammation and recurrence.

These findings highlight the potential of CFD to identify local airflow disturbances and subtle pressure variations that may underlie ECRS recurrence, providing insights for future therapeutic strategies.