The effect of exercise on the deposition of an inhaled aerosol

We investigated the regional deposition in the lungs, of an inhaled submicron aerosol at rest and during exercise in 13 normal volunteers of whom 5 were cigarette smokers. The degree of exercise (VO2 approximately 2 L/min) was chosen to simulate moderately heavy physical labour. Tracheobronchial and alveolar components of deposition were measured by comparing images immediately after inhalation of aerosol and 24 h later when mucociliary clearance was complete. At rest almost all deposition was alveolar (97%). The increase in total deposition on exercise was of similar order to the increase in ventilation. On exercise regional alveolar deposition became more even, although basal still exceeded apical deposition. Tracheobronchial deposition on exercise was increased in all zones but particularly in the upper zones, thereby contrasting with the base to apex gradient of parenchymal deposition. These changes were exaggerated in the smokers. The increased upper zone tracheobronchial deposition may have implications in regard to the pathogenesis of diseases caused by the inhalation of dusts and fumes.