Assessment of different clearance mechanisms of the lung using factor analysis

: Measurement of epithelial clearance over the lungs is always influenced by mucociliary transport since the lung is a 3-dimensional organ where ciliated and respiratory epithelia overlap. Factor analysis provides factor images and time-activity curves of extracted physiological factors corresponding to specific structures, even if these structures overlap. In 16 inhalation studies of 99m Tc-DTPA aerosol, factor analysis always extracted 2 factors with opposite temporal behavior, one corresponding to epithelial and one to mucociliary transport. Clearance rates measured over the lungs were significantly lower than epithelial transport-related factor curve values (1.35%/min vs 2.2%/min), but were identical with the clearance rates of the sum of both factors plus factor background. Factor analysis allows quantitative assessment of epithelial transport without interference of other clearance mechanisms and should be evaluated further in different pulmonary disorders.