The physiological evidence for static gas trapping in TOPD was lower IC (21.5% lower), higher FRC and higher ERV compared with subjects with COPD without this history, while no differences in TLC, RV and RV/TLC were observed.
Together, these findings suggest a combination of pathologies in TOPD. First is emphysema with gas trapping only evident on expiratory HRCT scans.
A second significant finding was the reduction in D[Lsub.CO] in subjects with TOPD. Although commonly reduced in COPD and correlated with the presence of emphysema, in our study of patients with TOPD, the D[L.sub.CO] was 17.7% lower than in the control group with COPD, although emphysema scores in these individuals were not significantly higher.