Aerosol transport in the human lung from analysis of single breaths

Experimental and theoretical results are presented for the single-breath inhalation of an aerosol with 0.5- and 1-micrometer particles of bis(2-ethylhexyl) sebacate droplets. Experimental results show that the recovery from the tidal volume decreases with increasing tidal volume and increases with increasing flow rate. The reserve volume recovery does not vary much with either flow rate or tidal volume. Experimental values for reserve volume recoveries for 1-micrometer particles were slightly larger than those for 0.5-micrometer particles, indicating intrinsic particle motion plays some role in the mixing process for larger particles. Calculated results from a convection-diffusion equation for the aerosol concentration are compared with the experimental results, with the aim of testing the hypotheses of the theoretical model. Detailed comparisons between theory and experiment for the exhalation profiles demonstrate that most of the mixing between the tidal and reserve volumes occurs in the alveolar region of the lung, as postulated in the model. Mechanical mixing in the upper airways plays a relatively minor role in the overall mixing process. Theoretical results for the recoveries show the same trends with tidal volume and flow rate as does experiment, and the agreement is good. Calculated values for the mixing of the tidal aerosol range from about 0.06 at a tidal volume of 400 cm3 to 0.23 at 2,000 cm3, and no variations with flow rate was found.