Respiratory drugs influence lung mucociliary clearance in central and peripheral ciliated airways

Radiolabelling of mucus and gamma-camera imaging techniques were utilized to differentiate mucociliary function in large central and small peripheral bronchi of man. Lung mucus clearance was analyzed for the entire right lung field and a peripheral region, which was representative of mucus clearance from airways distal to lobar bronchi. On control days, healthy subjects breathed monodisperse particles, average size 4.19 micrometers, and achieved central patterns of deposition with mouth breathing at rest. Matched deposition patterns were achieved on treatment days when isoetharine or isoproterenol influence on mucus clearance was measured and compared to control. Whole and peripheral lung clearances were increased by beta-adrenergic aerosol: isoetharine/control clearance ratios for whole and peripheral lung average 1.47 and 1.50, respectively; similar results were found for isoproterenol with ratios of 1.47 and 1.23, respectively. These data indicated that in healthy subjects the peripheral bronchi have the longest turn-over times for replacement of their mucous linings, and that these airways, like the larger airways of the trachea and main bronchi, can be stimulated by beta-adrenergic agents to increase their base-line flow of mucus.