Particle deposition in the nose related to nasal cavity geometry

A number of studies have been made to characterise the deposition-pattern of inhaled airborne particles in the nose. Common to all results has been considerable differences in deposition fractions between normal human subjects. It was the aim of the current study to improve our understanding of individual differences in nasal deposition of inhaled particles. Depositions were measured in ten adult normal subjects and were related to dimensional measurements by acoustic rhinometry. Five litres of a polydisperse aerosol (MMAD = 0.7 micron, sigma g = 1.7) were inhaled through one nostril only during 5 inspirations with flows of 10, 20, and 30 L/min with decongested mucosa. Increasing flow was found to increase the fraction deposited in the nose, while there was an inverse correlation between nasal deposition fraction and minimum cross-sectional area of the nasal cavity (Amin). Information based on acoustic rhinometry measurements significantly reduced the amount of unexplained variation between subjects in nasal deposition fraction. We conclude that an estimate of maximum linear air velocity, calculated as airflow divided by Amin, was the best single predictor of nasal deposition fraction, which was found to increase with increasing air velocity raised to a power of approximately 4/3.