Experimental measurements and empirical modelling of the regional deposition of inhaled particles in humans

Abstract

Regional deposition of inhaled particles was studied experimentally in a hollow cast of the human larynx-tracheobronchial tree extending through the first six branching levels, and in twenty-six non-smoker human volunteers in vivo. Results of the hollow cast study indicated a linear dependence of particle deposition efficiency on the Stokes number for aerosols with aerodynamic diameters>2 µm. Alveolar and total respiratory tract in vivo deposition in healthy non-smokers was minimal for particles of ∼0.4 µm, and alveolar deposition for mouthpiece inhalations peaked for particles of∼3 µm. A new anatomic parameter, the bronchial deposition size (BDS), is introduced to permit the classification of various individuals and populations according to their tracheobronchial deposition efficiencies. The average BDS's were 1.20 cm for 26 healthy non-smokers, 1.02 cm for 46 cigarette smokers, 0.90 cm for 19 clinical patients being treated for obstructive lung disease and 0.60 cm for six severely disabled patients.