Evaluation of droplet velocity and size from nasal spray devices using phase Doppler anemometry (PDA)

To determine aerosol deposition during the inhalation drug delivery, it is important to understand the combination of velocity and droplet size together. In this study, phase Doppler anemometry (PDA) was used to simultaneously characterize the aerosol velocity and droplet size distribution (DSD) of three nasal spray pumps filled with water. Thirteen sampling positions were located in the horizontal cross-sectional area of the nasal spray plumes at a distance of 3 cm from the pump orifice. The results showed droplet velocities near the center of the spray plume were higher and more consistent than those near the edge. The pumps examined showed significant differences in their aerosol velocity at the center of the spray plume, which suggest that this metric might be used as a discriminating parameter for in vitro testing of nasal sprays. Droplet size measurements performed using PDA were compared with results from laser light scattering measurements. The ability of PDA to provide simultaneous measurements of aerosol velocity and size makes it a powerful tool for the detailed investigation of nasal spray plume characteristics.