EFFECTS OF SMOKING ON BRONCHIAL CLEARANCE OF TECHNETIUM-99M-DTPA AND INDIUM-113M-DTPA

In asymptomatic smokers, epithelial permeability in the distal lung re gions is increased. To date, the effect of smoking on the epithelial p ermeability in proximal lung regions is stilt debated. The measurement of bronchial clearance of inhaled radiolabeled diethylene-triaminepen taacetic acid (BC-DTPA) can be used to assess epithelial permeability of proximal bronchi, but there are two potential limitations to this m ethod: in vivo breakdown of Tc-99m-DTPA in smokers and mucociliary tra nsport of DTPA. Methods: Eight nonsmokers and eight asymptomatic smoke rs were studied. We used a spinning disk system to generate an aerosol of large particles of Tc-99m-DTPA or In-113m-DTPA (MMAD 6.3 mu m). To measure the bronchial clearance of Tc-99m-DTPA and In-113m-DTPA, we a nalyzed the perihilar regions of the lung. To determine the contributi on of mucociliary transport, we measured the activity over a tracheal region of interest (ROI) in eight nonsmokers. Results: Technetium-99m- DTPA bronchial clearance did not differ in smokers (1.16 +/- 0.54 %/mi n; mean +/- s.d.) or nonsmokers (1.29 +/- 0.51 %/min; ns). The In-113m -DTPA bronchial clearances in nonsmokers (1.24 +/- 0.51 %/min) and in smokers (1.01 +/- 0.66 %/min) were similar to the Tc-99m-DTPA bronchia l clearances (ns). in the tracheal ROI, we found no increase in activi ty. Conclusion: In smokers, BC-DTPA was not increased compared to nons mokers. In contrast to distal lung regions, there was no evidence of b reakdown of the Tc-99m-DTPA complex in the proximal regions of smokers ' lungs. Mucociliary clearance does not significantly contribute to BC -DTPA.