Aerosol-derived airway morphometry (ADAM) in patients with lung emphysema diagnosed by computed tomography--reproducibility, diagnostic information and modelling.

Gravitational deposition of monodisperse particles can be used to determine effective airway diameter (EAD). The aim of our study was to assess intraindividual variability of EAD in healthy subjects and patients with emphysema, to compare EAD in patients with different degree and type of emphysema, and to evaluate whether parametric or model analysis would improve the results. EAD was measured vs volumetric lung depth (LD) in 11 healthy subjects (FEV subset1 107%pred) and 41 patients with emphysema (FEV subset1 60%pred; 8/9/24 mild/moderate/severe, 18/7/16 centriacinar/panacinar/bullous according to HRCT). Repeated measurements in LDs of 6-30% showed coefficients of variation of 7.0-10.4% in healthy subjects and 8.3-11.9% in emphysema. Average EAD in 10-16% LD was increased in emphysema, in particular moderate and severe (p<0.05, each). The slope of EAD in 10-16% LD differed between healthy subjects and emphysema, especially bullous and centriacinar. Patients with severe emphysema also showed a different slope compared to mild emphysema and controls. The parameters of the power function used for data fitting also showed differences between controls and emphysema, as well as between centriacinar vs panacinar and bullous emphysema. In a three-compartment lung model only the diameter of the intermediate compartment was enlarged in emphysema. We conclude that in using aerosol-derived airway morphometry, reproducibility of repeated measurements is acceptable. Average values and slopes of the EAD curve, as well as a power function for data fitting, were sensitive in the detection of type and severity of emphysema. In contrast, application of a lung model did not improve the results.