Nasal Cycling and Its Effects on Olfactory Drug Deposition

Introduction: Nasal cycle is driven by temporal phases of congestion and decongestion of the nasal mucosa, which influence unilateral airflow partitioning between both nasal cavities. However, not much is known regarding how the phenomenon of nasal cycles impact the transport and distribution of intranasal drug delivery in the nasal airways. Thus, this study aims to investigate intranasal spray deposition patterns in the airway across different nasal cycling states.

Methods: Radiographic images of 24 adult subjects with healthy, normal nasal anatomy were used to reconstruct anatomically realistic airway models. Subjects were grouped according to degree of nasal cycling as Mid (MD; n=12), Mild (ML; n=6), or Extreme (EX; n=6). Nasal airflow and drug delivery simulations were done at a resting inspiration of 15L/min, 10mm spray released insertion, particle velocity 5 m/s, and plume angle of 70 degrees. Depositions in the anterior, olfactory cleft, and posterior airway regions were calculated. Pairwise comparisons were performed using Wilcoxon Rank Sum Test and effect sizes calculated using rank-biserial correlation (rb).

Results: Average (±Standard Deviation) depositions were: MD=65.85±6.55%, ML=67.07±5.89%, EX=66.10±4.66% for anterior region; MD=0.39±0.34%, ML=0.42±0.60%, EX=1.12±1.37% for olfactory cleft; and MD=10.83±5.68%, ML=10.26±6.07%, EX=8.47±3.99% posteriorly. Pairwise comparisons for all regions were nonsignificant. Anterior: MD vs ML p=0.62, rb=-0.15; MD vs EX p=0.96, rb=-0.04; ML vs EX p=0.70, rb=0.12. Similar results held for olfactory cleft and posterior airways.

Conclusions: On average, the anterior airway had the greatest deposition, while the olfactory cleft had the least. When comparing bilateral deposition across cycling states, no cycling state deposition was statistically significant from one another.