Characterization of deposition from nasal spray devices using a computational fluid dynamics model of the human nasal passages.

Many studies suggest limited effectiveness of spray devices for nasal drug delivery due primarily to high deposition and clearance at the front of the nose. Here, nasal spray behavior was studied using experimental measurements and a computational fluid dynamics model of the human nasal passages constructed from magnetic resonance imaging scans of a healthy adult male. Eighteen commercially available nasal sprays were analyzed for spray characteristics using laser diffraction, high-speed video, and high-speed spark photography. Steadystate, inspiratory airflow (15 L/min) and particle transport were simulated under measured spray conditions. Simulated deposition efficiency and spray behavior were consistent with previous experimental studies, two of which used nasal replica molds based on this nasal geometry. Deposition fractions (numbers of deposited particles divided by the number released) of 20- and 50-microm particles exceeded 90% in the anterior part of the nose for most simulated conditions. Predicted particle penetration past the nasal valve improved when (1) the smaller of two particle sizes or the lower of two spray velocities was used, (2) the simulated nozzle was positioned 1.0 rather than 0.5 or 1.5 cm into the nostril, and (3) inspiratory airflow was present rather than absent. Simulations also predicted that delaying the appearance of normal inspiratory airflow more than 1 sec after the release of particles produced results equivalent to cases in which no inspiratory airflow was present. These predictions contribute to more effective design of drug delivery devices through a better understanding of the effects of nasal airflow and spray characteristics on particle transport in the nose.