Regional Deposition in Human Lung of 2.5 μM Particles

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Abstract
Regional deposition in the lung of 111In-labelled Teflon particles with an aerodynamic diameter of 2.5 .mu.m 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 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.