Effects of Anatomy and Particle Size on Nasal Sprays

Abstract

Objective: Compare spray penetration past the nasal valve (NV) predicted for particle sizes at varying spray speeds using a computational fluid dynamics (CFD) model of the human nasal cavity with septal deviation on the left side and inferior turbinate hypertrophy on the right.

Method: Simulations using Fluent (ANSYS, Inc, Lebanon, New Hampshire) were carried out for 10 µm, 20 µm, 50 µm, or particle sizes following a Rosin Rammler Particle Size Distribution (RRPSD) ranging from 10-110µm. Spray speed was 1 m/s, 3 m/s, or 10 m/s; steady state inspiratory airflow rate was 15.7 L/min.

Results: Simulations predicted at least 2 times higher NV penetration on the right side (hypertrophic turbinate) than the left (septal deviation) for most particle sizes and spray speeds. Simulated penetration of 10 µm particles at 1 m/s was 100% with none escaping via the nasopharynx. At 3 and 10 m/s, more simulated 10µm particles escaped the nose than other sizes. Maximum penetration of RRPSD, 20µm, and 50µm particles was predicted to be 15%, 35%, and 12% on the left side, and 52%, 58%, and 56% on the right, respectively, occurring at 1m/s for RRPSD and 50 µm, and 3 m/s for 20 µm.

Conclusion: In the presence of a septal deviation, sprays containing 10 µm particles may have better penetration past the NV. Additionally, increasing spray speed (above 3m/s) appears to limit spray penetration, suggesting that patients should be discouraged from spraying medications forcefully, as this could limit penetration of the drug.