Elimination of test particles from the human tracheobronchial tract by voluntary coughing.

: The effect of coughing on the elimination of inhaled 6 micrometer radioactively tagged teflon particles in humans was studied by external measurements of the radioactivity retained in the lungs before and after 1--2 min of voluntary coughing. In six healthy subjects coughing produced no substantial elimination of the particles. Six out of eight patients with lung disease produced expectorate and also eliminated particles from the lungs by coughing. The other two patients had no phlegm, did not produce any expectorate and did not eliminate particles by coughing. An increased amount of tracheobronchial secretion thus seems to be necessary for coughing to be effective. In the patients, the elimination of particles by coughing was fairly reproducible, suggesting that the test model may be useful for investigation of the influence of physiological and pharmacological factors on the elimination process.