Regional Deposition in Human Lung of 2.5 μM Particles

Abstract

Regional deposition in the lung of¹¹¹ In-labelled Teflon particles with an aerody-namic diameter of 2.5 μm 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 (R_aw) 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 R_aw. 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-lifes of a few hours, e.g., ^99mTc, can be used in studies of regional lung deposition when mucociliary transport system has been stimulated.