IN-VIVO MEASUREMENTS OF NASAL AIRWAY DIMENSIONS AND ULTRAFINE AEROSOLDEPOSITION IN THE HUMAN NASAL AND ORAL AIRWAYS

Understanding the filtration efficiency of the nasal and oral airways is essential for assessing doses of inhaled particles to the extrathor acic region as well as to the lung. This paper presents in vivo measur ements of nasal airway dimensions and the extrathoracic deposition of ultrafine aerosols in 10 normal adult males. The nasal geometry of eac h subject was characterized using magnetic resonance imaging and acous tic rhinometry. The nasal and oral deposition efficiencies were measur ed for particles ranging from 4 to 150 nm at constant flow rates of 16 7 and 333 cm(3) s(-1). Results indicated that both nasal dimensions an d particle deposition varied significantly among individuals. Inter-in dividual variability in particle deposition was correlated with the wi de inter-individual variation of nasal dimensions measured by the tota l surface area, minimum cross-sectional area, and complexity of the ai rway shape. We concluded that the significant biological variability i n extrathoracic filtration of ultrafine aerosols must be considered in developing population-wide dosimetry of inhaled particles.