Computational study of the impact of nasal vestibule anatomy on nasal drug administration with nasal spray.

The nasal airway comprises a complex network of passages and chambers and plays an important role in regulating the respiratory system's functions. The nasal vestibule is the first chamber of the nasal airway. While variations in nasal vestibule geometries are known to exist between humans, details of their implications on how they may affect the efficacy of nasal drug delivery devices are less clear. In this study, an investigation into how geometrical variations in nasal vestibule could affect particle deposition was conducted to elucidate the role of the vestibule in respiratory physiology. MRI was used to image the nasal airway of 11 subjects. The vestibules in the subjects were reconstructed using 3D slicer, and integrated with a common nasal turbinate to isolate the complexities in flow behavior when subject-specific turbinates were used. This approach minimises the impact of anatomical variations downstream of the vestibule, allowing for a focused evaluation of the vestibule's specific role in airflow dynamics and particle deposition. Particle deposition was examined using a steady flow rate of 15 L/min. Results from this study show that airflow velocity is highest in the middle region of the nasal airway's cross-section, while the olfactory and turbinate regions experience relatively lower airflow. A significant relationship (P < 0.05) between the nostril area, vestibule surface-to-volume ratio and particle deposition was also determined for small particle sizes (10-15 μm), demonstrating the feasibility of tailoring nasal drug delivery efficacies in individuals by cross-examining their nostril area and vestibule surface-to-volume ratio.