Deposition of polydisperse aerosols in two glass models representing the upper human airways

The paper discusses the properties of models used to estimate the deposition of aerosols in human respiratory tract. The deposition equations used in these models differ from each other as well as from the theoretical deposition equations. In order to be able to evaluate the deposition equations, deposition experiments have been carried out with two models made of glass. The first model imitates the actual lung structure and the second model the lung model of Weibel (Morphometry of the Human Lung. Springer Verlag, Berlin (1963)). Both models consist of the mouth up to and including the 6th generation according to Weibel's model. The distribution of the deposition of two polydisperse aerosols in these models is measured with a radioactive method, using sup(99m)Tc as a tracer after a constant inhalation of 8.0 or 16.0 l/min. As a result the deposition in the mouth and oropharynx is ascribed to impaction while the deposition in the different generations can be explained by laminar sedimentation and diffusion. Using a division of the polydisperse aerosol into 13 monodisperse aerosols, the theoretical deposition is calculated. The results show that deposition in the different generations at these airflows is approximated within 25% using exact solutions for a laminar airflow. Including impaction, as calculated with formulae found in literature, values for the deposition are calculated which are much too high (between a factor of 1.9 and 14). It is concluded that the impaction is the main problem in explaining these results. (author)