Acute effect of inhaled salbutamol on mucociliary clearance in health and chronic bronchitis

We investigated in a double-blind study the acute effect of the inhaled beta 2-adrenergic agent salbutamol on mucociliary clearance in man. Subjects were 20 patients with chronic bronchitis (10 receiving the drug and 10 placebo) and 6 healthy individuals (3 receiving the drug and 3 placebo). Mucociliary clearance was evaluated after inhalation of a pressurized 99mTc-labelled a albumin aerosol (median mass aerodynamic diameter 2.85 microns). Particle deposition and clearance was determined by external recording with a large-field gamma camera and dedicated computer, for three consecutive hours without moving the subject. After 1 h baseline clearance recording the subject was given either salbutamol (500 micrograms) or vehicle alone from a commercial pressurized nebulizer; recording was then continued for a further 2 h (test period). Both patients and normals treated with salbutamol showed a significant increase in the rate of clearance when compared with their respective control group receiving placebo. Clearance rates (percentage activity cleared per hour) from the lungs in the hour after salbutamol inhalation averaged 33.1% +/- 13.5 (SD) per hour, for patients (control 12.2% +/- 5.6 (SD) per hour, p less than 0.001) and 16.1% +/- 4.3 (SD) per hour for normals (control 7.8% +/- 2.0 (SD) per hour, (p less than 0.005). Significant differences were also found in clearance rate before and after salbutamol inhalation in both treated groups. Cough events did not produce any significant effect on average mucociliary clearance. However, visualization of serial computer images in individual patients showed that cough may generate appreciable upward, downward or even lung-to-lung movements of radioactive boli.