Olfactory drug delivery with intranasal sprays after nasal midvault reconstruction

Conductive olfaction and nose to brain drug delivery are important processes that remain limited by inadequate odorant or drug delivery to the olfactory airspace. Primary challenges include anatomic barriers and poor targeting to the olfactory region. This study uses computational fluid dynamics to investigate the effects of nasal midvault surgery on olfactory drug delivery with intranasal sprays. Soft tissue elevation, spreader flaps, and spreader grafts were performed on two fresh cadaveric specimens, using computed tomography for airway reconstruction. Nasal airflow and drug particle transport simulations were performed under these conditions: inhalation rate (15, 30 L/min), spray velocity (1, 5, 10 m/s), spray location (top, bottom, center, medial, lateral), head position (upright, supine, forward, backward), and particle size (1-100 µm). Simulation results were used to calculate drug particle deposition to the olfactory airspaces and bulbs. Total olfactory deposition was < 5% but attained a maximum of 36.33% when sorted by particle size. There was no association between nasal midvault surgery and olfactory deposition. No single parameter or technique demonstrated superior olfactory deposition, but smaller particle size, slower spray velocity, and higher inhalation rate tended to optimize olfactory deposition, providing important implications for future intranasal spray and drug design to target the olfactory airspace.