Effect of salmeterol on mucociliary and cough clearance in chronic bronchitis

The effect of long acting beta(2)-adrenergic bronchodilators on impaired mucociliary clearance in chronic bronchitis is unknown. Using a radiolabeled aerosol (technetium-99m-labeled sulfur colloid) and gamma camera analysis, we measured the acute effect of salmeterol vs. placebo on mucociliary and cough clearance in mild-moderate chronic bronchitics (n = 14) over a 2h period. During the 1-1(1/2) h period of observation patients performed 60 controlled coughs on each study day. Average whole lung clearance through 1 and 2h after administration of salmeterol (42 microg) or placebo via metered dose inhaler (double-blinded, crossover design study) showed no significant difference between treatments. Similarly, for the specific period when cough was added to mucociliary clearance, there was no difference on whole lung clearance between treatments. However, when clearance from the peripheral region of the lung was assessed over the entire 2h period of observation, salmeterol provided a 30% enhancement of airway clearance compared to placebo, average peripheral 2h clearance (%) = 22 +/- 9 vs. 17 +/- 10 for salmeterol vs. placebo (P = 0.05 by paired analysis). Thus, in addition to its bronchodilating effects, salmeterol acutely enhances peripheral airway clearance of secretions in mild-moderate chronic bronchitis.