Validity of in vitro tests on aqueous spray pumps as surrogates for nasal deposition

Purpose. To determine whether deposition pattern is related to in vitro measurements of droplet size, plume geometry, and spray pattern between two different nasal spray pumps believed to have different performance characteristics. Methods. Ten healthy volunteers inhaled radiolabeled saline from two different spray pumps (pump A and pump B). Deposition pattern was quantified from lateral views of the nose by gamma scintigraphy, expressed as the ratio of anterior to posterior (I:O) and superior to inferior (U:L) deposition. Droplet size was determined by Malvern Mastersizer S. Spray patterns were determined at 2.5 and 5 cm from the tip of the spray nozzle. Two-dimensional images of the emitted plume were captured by high-speed still photography. Results. There were no significant differences in I:O or U:L ratios for pump A compared to pump B, indicating no significant differences in deposition pattern. The volume diameters, D-v10 and D-v50, were not statistically different for pump A compared to pump B. There was a significant difference in D-v90 between pump A and pump B, (86.9 +/- 5.8 mum and 77.4 +/- 2.4 mum, respectively; P < 0.001). The ratio of the longest to shortest diameter for the spray pattern with pump A was 1.26 +/- 0.06 at 2.5 cm and 1.44 +/- 0.08 at 5 cm. The ratio for pump B was 1.13 +/- 0.03 at 2.5 cm and 1.19 +/- 0.05 at 5 cm. Ratios at both heights were statistically different for pump A compared to pump B (P < 0.00002 and P < 0.000001, respectively) Plume geometry analysis indicated statistical differences in both the width (17.0 +/- 0.97 vs. 18.5 +/- 0.56 cm, respectively; p < 0.001) and the maximum length of the plumes (46.0 +/- 1.83 vs. 53.1 +/- 4.88 cm, respectively; p < .002). The differences in velocity of the plume and spray angle between the two pumps were not statistically different. Conclusions. Certain in vitro tests detected performance differences between the two pumps. However, these differences did not translate into different deposition patterns in vivo.