Sulfur dioxide and tracheobronchial clearance in man.

Tracheobronchial clearance was measured in nine healthy, nonsmoking adults. Technetium Tc 99m albumin aerosol (mass median diameter, 3 mu; geometric standard deviation, 1.6) was inhaled as a bolus under controlled conditions to achieve reproducible deposition in large airways. Each subject was studied in three seperate three-hour experiments: twice under control conditions and once exposed to 5 ppm sulfur dioxide (pollutant exposure after aerosol inhalation). Lung retention of activity was measured using a gamma camera interfaced to a data storage and retrieval system. The study showed that (1) Both deposition and clearance were highly reproducible in individuals in repeat control studies. (2) Acute exposure to 5 ppm sulfur dioxide had no significant effect (P greater than .05) on mucocillary clearance in resting healthy subjects, except perhaps for a small transient change (P=.05) after one hour. (3) Pulmonary function tests showed a decrease in maximal midexpiratory flow (P less than .01) but no other significant changes.