Can aerosol-derived airway morphometry detect early, asymptomatical lung emphysema?

The aerosol-derived airway morphometry technique (ADAM) can be used to assess non-invasively peripheral airspace dimensions. It has been shown that this technique can identify permanent peripheral airspace enlargement in patients with lung emphysema, but it is yet unknown if early stages of emphysema can be detected. In this study, 89 aluminum welders were investigated. Although all (except two subjects) showed normal spirometry, in 29% of the subjects visual signs of early emphysema were observed with high-resolution computed tomography (HRCT) in a previous study. Using the ADAM technique, 28% of the subjects showed increased peripheral airspace dimensions. However, both groups with positive findings overlapped only in about half of the cases. Peripheral airspace dimensions correlated significantly with the mean lung density calculated from the HRCT scans, and lung density was significantly decreased in the group with increased airspace dimensions. The poor overlap of the positive findings observed with both techniques can be explained if it is considered that the visual HRCT technique and ADAM focus on different aspects of emphysematous changes in the lungs. Whereas visual HRCT is a powerful tool to identify focal changes in lung density but cannot detect mild homogeneous emphysema, ADAM delivers a measure for homogeneously distributed emphysema but cannot detect focal emphysema or regions with emphysema which are badly ventilated. Since ADAM is easy to perform, non-invasive, and can be repeatedly applied to human subjects without radiological concerns, this technique might become a useful tool for the detection and monitoring of lung emphysema in occupational medicine, epidemiology, and pharmaceutics.