Human Nasal Passage Particle Deposition: The Effect of Particle Size, Flow Rate, and Anatomical Factors

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Abstract
This study determined the effect of particle size, flow rate, nostril shape, and nasal passage geometry on nasal particle deposition efficiency (PDE) in ten healthy, nonsmoking adults (seven males, three females). A polydispersed (1–10-μm diameter) aerosol was drawn by unidirectional flow in through the nose and out through the mouth. Three constant flow rates of 15, 25, and 35 l/min were used in this study. The nasal PDE was calculated by measuring size and concentration of aerosol entering the nose (C in) and exiting the mouth (C out), and was defined as (C in-C out)/C in for each particle size and flow rate. A mixed nonlinear model was used to fit the PDE to an equation using particle aerodynamic diameter, flow rate, nostril length to width ratio (ellipticity, E), and minimum nasal cross-sectional area (A min). Statistical analyses show that all above factors affect particle deposition in the nasal passage. Even after inclusion of the above factors, there remains a large intersubject variation in deposition. Future studies should evaluate the effect of middle and posterior nasal passage geometry on nasal particle deposition.