On computational fluid dynamics models for sinonasal drug transport: Relevance of nozzle subtraction and nasal vestibular dilation

Generating anatomically realistic 3‐dimensional (3D) models of the human sinonasal cavity for numerical investigations of sprayed drug transport presents a host of methodological ambiguities. For example, subject‐specific radiographic images used for 3D reconstructions typically exclude spray bottles. Subtracting a bottle contour from the 3D airspace and dilating the anterior nasal vestibule for nozzle placement augment the complexity of model building. So we explored the question: how essential are these steps to adequately simulate nasal airflow and identify the optimal delivery conditions for intranasal sprays? In particular, we focused on particle deposition patterns in the maxillary sinus, a critical target site for chronic rhinosinusitis. The models were reconstructed from postsurgery computed tomography scans for a 39‐year‐old Caucasian male, with chronic rhinosinusitis history. Inspiratory airflow patterns during resting breathing are reliably tracked through computational fluid dynamics–based steady‐state laminar‐viscous modeling, and such regimes portray relative lack of sensitivity to inlet perturbations. Consequently, we hypothesized that the posterior airflow transport and the particle deposition trends should not be radically affected by the nozzle subtraction and vestibular dilation. The study involved 1 base model and 2 derived models; the latter 2 with nozzle contours (2 different orientations) subtracted from the dilated anterior segment of the left vestibule. We analyzed spray transport in the left maxillary sinus for multiple release conditions. Similar release points, localized on an approximately 2 mm × 4.5 mm contour, facilitated improved maxillary deposition in all 3 test cases. This suggests functional redundancy of nozzle insertion in a 3D numerical model for identifying the optimal spray release locations. Identifying optimal intranasal spray release points through CFD modeling presents methodological ambiguities on the inclusion of spray nozzle in the CT‐based 3D reconstructions. We simulated spray transport in 3 anatomically realistic models from the same subject: 1 base model and 2 derived models (with lateral vestibular dilation and nozzle subtraction in 2 different orientations). Similar release points facilitated improved target site particle deposition (TSPD) in all 3 test models, indicating that TSPD trends are less sensitive to nozzle‐induced inlet perturbations.