Lung clearance mechanisms in obstructive airways disease.

Using radioaerosol inhalation lung cinescintigraphy, pulmonary clearance mechanisms were studied in 21 patients with obstructive airways disease. In none of them did we find homogeneous deposition of inhaled radioaerosol in the lungs, or a steady, constant, axial, and cephalad transport of radioactivity in the major airways. Of the 21 patients, 14 showed temporary but frequent stopping and starting of radioactivity in the airways in the course of lung clearance; in ten there was reversal of flow; in five migration of radioactivity from one bronchus into the opposite, bypassing the trachea and often followed by shuttling between right and left bronchi; and in four there was spiral or zigzag transport of radioactivity. The overall lung retention ratio in the first 2 hr was not abnormal, but the airway deposition ratio was significantly above normal, and airway clearance efficiency was below. The alveolar deposition ratio was also significantly smaller in these patients.