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Generating anatomically realistic three-dimensional (3D) models of the humansinonasal cavity for numerical investigations of sprayed drug transportpresents a host of methodological ambiguities. For example, subject-specificradiographic images used for 3D reconstructions typically exclude spraybottles. Subtracting a bottle contour from the 3D airspace and dilating theanterior nasal vestibule for nozzle placement augment the complexity ofmodel-building. So, we explored the question: how essential are these steps toadequately simulate nasal airflow and identify the optimal delivery conditionsfor intranasal sprays? In particular, we focused on particle depositionpatterns in the maxillary sinus, a critical target site for chronicrhinosinusitis (CRS). The models were reconstructed from post-surgery computedtomography scans for a 39-year-old Caucasian male, with CRS history.Inspiratory airflow patterns during resting breathing are reliably trackedthrough CFD-based steady state laminar-viscous modeling and such regimesportray relative lack of sensitivity to inlet perturbations. Consequently, wehypothesized that the posterior airflow transport and the particle depositiontrends should not be radically affected by the nozzle subtraction andvestibular dilation. The study involved 1 base model and 2 derived models; thelatter two with nozzle contours (two different orientations) subtracted fromthe dilated anterior segment of the left vestibule. We analyzed spray transportin the left maxillary sinus for multiple release conditions. Similar releasepoints, localized on an approximately 2mm-by-4.5mm contour, facilitatedimproved maxillary deposition in all three test cases. This suggests functionalredundancy of nozzle insertion in a 3D numerical model for identifying theoptimal spray release locations.

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