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Variability of tracheobronchial clearance in healthy non-smoking subjects.

Tracheobronchial clearance was measured twice in 10 healthy non-smoking volunteers to evaluate inter- and intrasubject variability, using a radio-aerosol technique (5 microns 99mTc-labelled polystyrene particles). By means of two detectors radioactivity in the lungs was measured at regular intervals for 6 h and once more 24 h after inhalation. The decrease in radioactivity after correction for background activity, isotope decay and 24-hour retention was assumed to reflect tracheobronchial clearance. Among other parameters to quantitate the results of these tests, the area under the retention curve up to 6 h after inhalation (AUC-6) was calculated. The intersubject coefficient of variation (COV) using the AUC-6 was 31%. The intrasubject COV of the AUC-6 was 11%. These results compare favourably with those reported by others using different techniques. It is concluded that the intrasubject variability of tracheobronchial clearance as measured by this technique is small.