Pulmonary clearance of inhaled 99Tcm-DTPA: significance of site of aerosol deposition

The aim of this study was to analyse how changes in the site of 99Tcm-DTPA aerosol deposition between central and peripheral parts of the lung influence routine measurement of pulmonary clearance of 99Tcm-DTPA(PC1). The study was performed in six'never-smokers' and 10 smokers with bronchial hypersecretion. Changes in aerosol deposition was accomplished by changing the aerosol particle size and the velocity by which the subjects inhaled the particles. In the smokers with bronchial hypersecretion there was a significantly smaller PC1 after central deposition than after peripheral deposition, while in the never-smokers, significance was not reached. The smokers with bronchial hypersecretion had significantly higher PC1 than the never-smokers when the 99Tcm-DTPA had been deposited in the peripheral parts of the lung, but at the examination of central deposition, the difference was no longer significant. It is concluded that in smokers with bronchial hypersecretion, measurement of regional PC1 is influenced by the site of 99Tcm-DTPA deposition in the lung. (author)