THE MACROTRANSPORT OF AEROSOL-PARTICLES IN THE LUNG - AEROSOL DEPOSITION PHENOMENA

The macrotransport model of lung dispersion (Edwards, 1994) is generalized to incorporate phenomena involving the nonconservation of gas and/or aerosol species in the airways and acini of the human lung during a single breath. The three principal parameters measured in single-breath gas or aerosol bolus dispersion experiments, namely, net deposition rate ((K) over bar*), mean bolus velocity ((U) over bar*) and effective dispersion coefficient (D) over bar*), are theoretically determined in terms of the detailed microtransport, branch-level phenomena underlying them. Explicit formulas are provided for the macroscale coefficients ((K) over bar*, (U) over bar*, (D) over bar*). Additionally, a formula is provided for a coefficient (A) over bar* that serves to characterize a novel ''apparent initial condition'' to be imposed upon the aerosol concentration profile as viewed from its coarse-grained level. Numerical calculations are made in the case of aerosols. These are based upon a symmetrical Weibel model A geometry, and employ the deposition model of Landahl (1950) for assigning constitutive laws to the branch-level deposition-rate parameters that underly the theory. Branch-level dispersion coefficients are described by an axial-streaming constitutive law, as in the previous contribution, while taking explicit account of the diminution of axial streaming caused by aerosol deposition. Comparison is made with the aerosol bolus experimental data of Heyder et al. (1988) and Anderson rt al. (1989). Predictions of net aerosol deposition in the human lung as a function of aerosol particle size are compared with predictions made on the basis of former aerosol-deposition theories, as well as with additional aerosol-deposition data appearing in the literature. Very good agreement is found for all of these comparisons.