Regional deposition in human lung of 2.5 microM particles

Regional deposition in the lung of 111In-labelled Teflon particles with an aerodynamic diameter of 2.5 micron was studied in eight healthy nonsmokers. The particles were inhaled at 0.5 l/sec with maximally deep breaths. Bronchoconstriction was induced by inhalation of a methacholine bromide aerosol, for one exposure series before (provocation experiment) and for one exposure series after (control experiment) inhalation of the Teflon particles. Airway resistance (Raw) was measured with a whole-body plethysmograph before and after the induction of bronchoconstriction and increased on an average by a factor of 3-4. The total lung deposition, in percent of the inhaled radioactivity, was 83 +/- 6% (mean +/- SD) for the control experiment and 84 +/- 5% for the provocation experiment. Alveolar deposition, estimated as the percentage retention of lung deposition after 24 hrs (Ret24), was significantly lower in the provocation experiment than in the control experiment, 42 +/- 10% and 77 +/- 12%, respectively. Ret24 varied greatly among the subjects in the control experiment; for example, individual tracheobronchial deposition varied by a factor of 5. Ret24 was not related to FEV1, FVC or Raw. The Ret24 values in the two exposure series correlated significantly indicating an individual factor. Retention at 3 and 24 hrs correlated strongly, r = 0.94. This implies that radionuclides with half-lives of a few hours, e.g., 99mTc, can be used in studies of regional lung deposition when mucociliary transport system has been stimulated.