Deposition of Ultrafine Aerosol Particles in a Human Tracheobronchial Cast

Total depositions in a human tracheobronchial cast were measured for ultrafine monodisperse aerosols below 0.1μm in diameter at flow rate of 4, 10 and 20l/min of constant and cyclic flows. The cast model consisted of the trachea and bronchial airways with branching generations from 4 to 10. At 20l/min constant flow, the inspiratory deposition efficiencies were 5% and 44% for 0.1 and 0.00475μm size particles, respectively. The deposition efficiency increased with decreasing particle size and flow rate. Compared with the inspiratory deposition, the expiratory deposition efficiencies were slightly higher for particles below 0.01μm. The deposition efficiencies under cyclic flow were found to be almost the same as those under constant flow having equivalent mean flow rate. It was also observed that varying the tidal volume, but keeping the minute volume constant (i. e., having the same mean flow rate), has little effect on deposition of the ultrafine aerosol particles.