EFFECT ON SINGLE-BREATH WASHOUT AND LUNG-FUNCTION OF ELASTASE-INDUCEDEMPHYSEMA IN RATS

Lung volumes, diffusing capacity (DL(CO)), quasi-static pressure-volum e curves (P-V), forced expiration (FE) and He-SF6 single-breath washou t (SBW) were performed in Wistar rats with emphysema induced by differ ent doses of pancreatic elastase in saline, instilled intratracheally 6 wk prior to the tests. Emphysema was quantitatively assessed by mean linear intercept (Lm) measurements on 5-mum lung sections. Lung volum e, P-V curve, and FE dependence on Lm, as well as the nonsignificant d ependence of DL(CO) on Lm, are generally similar to results reported b y others. The most interesting observation concerns the SBW: N2 slopes of the alveolar plateau, compared for identical lung volumes, did not change with the degree of emphysema. By contrast, the He-SF6 slope di fference did depend significantly on the degree of emphysema. Based on the diffusion front theory, the present work suggests that in rats wi th elastase-induced emphysema, the phase III slope modifications relat e mainly to elastic and not to structural alterations.