Mucociliary clearance of deposited particles from the human lung: intra- and inter-subject reproductivity, total and regional lung clearance, and model comparisons.

The intra- and inter-subject reproducibility of pulmonary mucociliary clearance was investigated in nine healthy male subjects following deposition of an aerosol of 7.9 microns aerodynamic diameter iron oxide particles labeled with TC-99m. The results have been analyzed for both total bronchial clearance and for clearance from areas representing central (Zone I), mid (Zone II), and peripheral (Zone III) regions of the lung. The observed clearance rates were compared to the predictions of a mathematical model for lung clearance based on Weibel's dicotomous branching system. The results for total bronchial clearance showed an average TB120 (percent cleared in 2 hr) of 57%, while the average TB120 for Zone I, II, and III was 56%, 62%, and 48%, respectively. The mean half-times (times required to clear 50% of the deposited activity) for the total bronchial clearance and for Zones I, II, and III were 1.90 hr, 1.97 hr, and 1.70 hr and 2.62 hr, respectively. Total bronchial and regional clearance was reproducible (P = .05) within subjects, but significant variation was observed among subjects. The predictions of the mathematical model for total bronchial clearance are in good agreement with the experimental results. However, the experimental clearance rate was slower in Zone I, and faster in Zone II and III than is predicted by the model. The implications of these results are discussed.