Exact analysis of aerosol deposition during steady breathing

Using a trumpet lung model, a transport equation is derived for an aerosol breathed into and out of the human airways. The partial differential equation is solved exactly using the method of characteristics. From this solution, the deposition of particles along the airways is obtained for steady breathing with and without pause. The total and regional depositions for particle sizes ranging from 0.01 μm to 10 μm aerodynamic diameter are calculated for Weibel's lung model, and they compare satisfactorily with the existing experimental data. The effects of the rest lung volume and breathing pattern on the total and regional depositions are also determined in order to explain the observed intersubject variability. Comparison between the present results with that recommended by the Task Group on Lung Dynamics shows that the present pulmonary deposition is considerably lower. while the tracheobronchial deposition differs only slightly.