Effect of flow-limiting segments and cough on particle deposition and mucociliary clearance in the lung.

Abstract

Functional narrowing of airways at flow-limiting segments may explain the patterns of aerosol deposition and impaired mucociliary clearance observed in patients with lung disease. Using intact dogs, we studied the effects of flow limitation (cough) on the regional deposition of inhaled particles as they left the lung during forced expiration. When compared to passive expiration, cough produced a significant increase in the deposition of 1-μm particles in the region immediately downstream from the flow-limiting segment (p < 0.05). Total deposition at the flow-limiting segment, although increased with cough, was unaffected by gas density or driving pressure. Deposition over the whole lung excluding the flow-limiting segment was unchanged during flow limitation. In a separate group of animals, the effect of cough on tracheal mucociliary clearance was assessed. Using radioactive saline droplets, measurements of tracheal mucociliary clearance were made before and after 50 to 100 coughs. In individual dogs (n =...