DEPOSITION AND CLEARANCE IN LARGE AND SMALL AIRWAYS IN CHRONIC-BRONCHITIS

Tracheobronchial clearance was studied twice in 16 patients with chron ic obstructive bronchitis after inhalation of 6 mu m (aerodynamic diam eter) monodisperse Teflon particles labeled with In-111. At one exposu re the particles were inhaled at an extremely slow flow, 0.05 L/s; at the other they were inhaled at a normal flow, 0.5 L/s. Theoretical cal culations and experimental data in healthy subjects indicate particle deposition mainly in the smallest ciliated airways using 0.05 L/s, i.e ., in the bronchiolar region, and an enhanced deposition in larger air ways using 0.5 L/s. Lung retention was measured at 0, 24, 48, and 72 h . Clearance was significant every 24 h for both exposures (p <.05). Th e fractions of retained particles were significantly larger for partic les inhaled at 0.05 L/s compared to 0.5 L/s at all points of time (p < .001). Compared to healthy subjects, the retained fractions of deposit ed particles were larger in patients with bronchitis breathing at 0.05 L/s, but smaller with breathing at 0.5 L/s (p <.01). Significant rela tionships were found between lung retentions and airways resistance (R aw) at 0.5 L/s. r=-.68 (p <.01), but not at 0.05 L/s, and between lung retention at 24 h and weight of expectorated sputum at 0.05 L/s, r=-5 0 (p <.05). There was, furthermore, an almost significant relationship between sputum volume and rate of tracheobronchial clearance between 0 and 24 h (in percentage of the total amount cleared during 72 h) at 0.05 L/s, r-.42 (p=.05). The results indicate that in patients with ch ronic bronchitis overall clearance of particles in small airways is in complete, as compared to larger airways. An increased amount of mucus, however, seemed to improve clearance of peripherally deposited partic les, possibly by making cough more effective in small airways.