Deposition and Clearance in Large and Small Airways in Chronic Bronchitis

Abstract

Tracheobronchial clearance was studied twice in 16 patients with chronic obstructive bronchitis after inhalation of 6 microns (aerodynamic diameter) monodisperse Teflon particles labeled with 111In. At one exposure 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 calculations 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 airways using 0.5 L/s. Lung retention was measured at 0, 24, 48 and 72 h. Clearance was significantly every 24 h for both exposures (p < .05). The fractions of retained particles were significantly larger for particles 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 deposited 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 relationships were found between lung retentions and airway resistance (Raw) 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 = -.50 (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 chronic bronchitis overall clearance of particles in small airways is incomplete, as compared to larger airways. An increased amount of mucus, however, seemed to improve clearance of peripherally deposited particles, possibly by making cough more effective in small airways.

Long-term clearance from small airways decreases with age

“…In an earlier study, a relationship was found between FEV1 values and clearance for subjects with chronic bronchitis [23]. Subjects with cystic fibrosis and FEV1 ,70% were found to have worse long-term clearance compared with those with FEV1 .70% [36].…”

“…Immediately after inhalation, and 24 h later, radioactivity was measured using two 127651-mm NaI detectors fitted with collimators [21][22][23][24][25][26]. The c-spectra from each detector were acquired separately.…”

“…the bronchioles, using rather large particles (6 mm) and an extremely slow inhalation flow (0.05 L?s -1 ). Calculations of deposition using different theoretical models indicate that a major fraction of the particles should deposit in small ciliated airways [20][21][22][23]. Another advantage of using this technique is that the regional particle deposition is independent in respect to airway constriction [24].…”

Long-term clearance from small airways in patients with cystic fibrosis

“…Sample size calculation based on variability data from the pooled SD in a previous study comparing clearance between healthy subjects and patients with chronic bronchitis [19], showed a demand of 12 individuals in each group to detect a difference of one SD with a power of 80%. The authors were finally able to recruit 11 CF patients.…”

Clearance in Small Ciliated Airways in Allergic Asthmatics after Bronchial Allergen Provocation

“…By inhaling rather large aerosol particles (6 µm) extremely slowly (0.05 liter/s), deposition by sedimentation takes place mainly in the small ciliated airways due to the prolonged transit time. Since deposition in these airways is practically independent of airway resistance, clearance data can be compared in healthy subjects [6]and patients with airway obstruction [9, 10, 11]. In a recent study, we found that particles clear equally well from the bronchiolar region in a group of healthy subjects and asthmatics on regular treatment with anti-inflammatory drugs, i.e.…”