Effect of Bronchodilators on Mucociliary Clearance in Normal Adults

Daily bronchodilator therapy with multiple agents is frequently utilized in patients with obstructive pulmonary disease to improve lung function. These drugs have also been shown to stimulate mucociliary activity in–vitro and in–vivo. To assess clearance differences between normal subjects and obstructed patients, the direct effects of theophylline and β-agents must be determined. In a single blind, placebo controlled study, the effects of oral theophylline, and oral and inhaled albuterol on mucociliary clearance were studied after a seven day regimen designed to duplicate the usual schedule followed by our patients. In seven normal subjects, clearance was assessed using a gamma camera by measuring the retention of inhaled radioaerosol over 2 hours and again at 24 hours. Radioaerosol deposition patterns were carefully matched between studies by varying the inspiratory flow. Although significant bronchodilation was observed following drug therapy, whole lung retention was not different on drug vs. placebo study days. We also confirmed our ability to detect mucociliary clearance changes due to β-adrenergic stimulation. Two subjects had repeat measurements of mucociliary clearance during which aerosolized isoproterenol was inhaled. As expected, whole lung retention was decreased in these subjects. Therefore, although certain bronchodilators have immediate stimulatory effects on mucociliary clearance, daily use does not change the time course of retention.