Lobar distribution of emphysema in computed tomographic densitometric analysis.

RATIONALE AND OBJECTIVES

The aims of this study were to determine the extent of emphysema in individual lobes and to investigate whether the lobar distribution of emphysema influences pulmonary function.

METHODS

Helical CT and pulmonary function tests were performed in 50 emphysema patients. Percentages of low attenuation volume (extent of emphysema) were calculated for each lobe by using CT densitometric analysis.

RESULTS

The extent of emphysema of the whole lung in these patients was 44%. Airflow limitation (r = -0.82, P<0.0001) and residual volume (r = -0.52, P<0.01) were closely correlated with the extent of emphysema in both lower lobes. Diffusing capacity (r = -0.61, P<0.0001) was closely correlated with the extent of emphysema in both upper lobes. On the basis of the lobar distribution of emphysema as determined by CT densitometry, we divided these emphysema patients into predominantly upper-lobe disease and predominantly lower-lobe disease groups. The predominantly lower-lobe disease group had significantly greater severe airflow limitation (P<0.0001), greater residual volume (P<0.01), and greater total lung capacity (P<0.05) than did the predominantly upper-lobe disease group.

CONCLUSIONS

CT densitometry showed a distinct lobar distribution of emphysema. Pulmonary function is significantly different between predominantly upper- and lower-lobe emphysema groups.