Pulmonary function tests versus computed tomography in sheep with experimental emphysema

The authors explored the relative utility of pulmonary function tests (PFTs) and computed tomography (CT) to characterize the progression of papain induced emphysema in sheep (n = 12). PFT included plethysmography (FRC(pleth)), helium dilution (FRC(He)), and expired reserve volume (ERV). Following papain, FRC(pleth) and FRC(He) were unchanged; ERV decreased hence residual volume increased significantly (RV + 270 mL, +86%, P = .02). In contrast, FRC by CT increased in 10 of 12 sheep (+264 mL +21%, P = .008). We conclude that plethysmography was insensitive to emphysema, but the effect on ERV (i.e., trapped gas volume) and FRC by CT were very similar, and in line with the morphologic changes in this animal model.