Spatial and temporal characterization of droplet diameter and velocities of a nasal spray atomization

Nasal sprays can deliver drugs topically to the nasal cavity and, alternatively, to the vascular system via the nasal epithelium, avoiding painful injections. The atomized spray characteristics can be optimally controlled for the desired parameters such as spray plume, cone angle, droplet velocity and droplet size distribution to target specific locations in the nasal cavity. These parameters have been investigated through computational simulations to evaluate the spray performance within the nasal cavity, however there is a lack of experimental measurements providing three-dimensional velocity data for nasal sprays. This study aims to address key elements of this gap using Phase Doppler Particle Analysis (PDPA) to measure both the droplet size and three-dimensional velocity from two over-the-counter nasal spray devices actuated with a pneumatic device delivering actuation forces equivalent to averaged pediatric, adult, and a maximum adult exertion. In addition to providing experimental data for verifying CFD simulations, this study provides multiple, and some unique, presentations of characterizing the nasal spray velocity and size behavior. Multiple new conclusions were drawn from this study, including a demonstration that the spray droplet axial velocity is the dominant velocity component, followed by radial velocity. Tangential velocity exists but is negligible by comparison. Finer droplets tended to move slower and were predominantly found in the spray core (although this may not be the case with a fluid of higher viscosity). Larger, faster droplets are found near the spray's edge in the pressure-swirl nasal sprays. The mean resultant velocity between both devices at 15 mm from the nozzle tip, actuated at the mean adult force was 16.9 m/s. The mean D32 and Dv50 of both devices at the mean adult actuation force was 23.0 mu m and 80.0 mu m, respectively.