CALCULATED DEPOSITION OF INHALED PARTICLES IN THE AIRWAY GENERATIONS OF NORMAL SUBJECTS

Detailed regional deposition of inhaled particles in the human lung is calculated for individual airway generations. The calculations are based on Landahl's deposition model as applied to the morphometric lung model of Weibel. The authors consider primarily deposition patterns of iron oxide particles with diameters ranging between 1 and 10 μm, but they also calculate patterns of deposition for bis(2-ethylhexyl) sebacate particles with diameters as small as 0.2 μm. Good agreement is obtained between predicted values and observed values for alveolar retention of inhaled iron oxide particles with 64 and 20% of total deposition predicted to occur in nonciliated airways for 2- and 5-μm particles, respectively. This is compared with 48 ± 9 and 27 ± 10% for the measured values. Calculated values for total lung deposition of small bis(2-ethylhexyl) sebacate particles agree well with experimental data. The calculations show a minimum in deposition occurring for particle diameters of 0.5 μm, which is in agreement with observations. A calculation of surface concentration of deposited 7.9-μm aerodynamic particles reveals a very large concentration occurring at airway generation four. This observation is considered in light of observations that bronchial carcinomas occur in this vicinity of the lung.