Particle-wall interaction computational model for nasal drug delivery considering mucus layer
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Inflammatory upper airway conditions, such as rhinosinusitis and laryngitis, impact approximately 20% of the global population. Inhalation therapy, including nasal spray, offers a promising avenue for treating such respiratory diseases. To enhance treatment efficacy, it is essential to comprehend how drug particles travel across the nasal cavity, interact with its walls, and ultimately deposit within the upper airways. This study introduces a computational model for the interaction between solid particles and nasal cavity walls. Unlike conventional approaches that assume a sticking or "deposit-on-touch" condition, our model accounts for the presence of the mucus layer coating the nasal cavity walls. In our model, a critical collision velocity criterion, based on that proposed by Ohsaki et al., determines whether the particle deposits or rebounds upon colliding with the wall. In cases of rebound, the collision angle is calculated based on the surface roughness characteristic of the mucus layer. The particle then continues its trajectory within the nasal cavity, gradually losing kinetic energy until it meets the deposition criterion. The efficacy of the particle-wall collision rebound model was assessed against experimental results using the same nasal cast geometry (from a 9-year-old patient), for the flow rates of 15L/min and 60L/min. The proposed model significantly enhances the accuracy of particle deposition, demonstrating a high level of consistency between the computational predictions and experimental observations.
