24-h and 48-h Retention of 5 m Polystyrene Particles in Relationship to Lung Function and Inhalation Flow Rate

Abstract

Lung retention of insoluble Tc-99m particles was measured at 24-h and 48-h in subjects of widely varying lung function. In 10 tests out of 58, clearance between 24-h and 48-h accounted for 10 to 26% of the initial lung deposit, presumably reflecting a continuing tracheobronchial clearance. Retention was analysed relative to lung function for three groups of tests: A, mean inhalation flow rate 20–241/min (n = 17); B, 25–301/min (n = 20); C, 31–381/min (n = 21). Within each group, 48-h retention correlated strongly with forced expiratory volume in 1 s(r > 0.84, p 0.81, p < 0.001). Differences of slope and position between the regression lines for the three groups suggested 48-h retention falling (as expected) with increasing inhalation flow rate in subjects with good lung function —but not in subjects with poor lung function. A substantial fraction of 48-h retention in the latter may represent impactional deposition at tracheobronchial sites.