HYSTERESIS RATIO - A MEASURE OF THE MECHANICAL EFFICIENCY OF FIBROTIC AND EMPHYSEMATOUS HAMSTER LUNG-TISSUE

Publisher Website
Google Scholar
Abstract
To evaluate the viscoplastoelastic properties of hamster lungs, a transpulmonary pressure of 25 cm H2O (TLC25(S)), quasistatic lung compliance (CstL(S)), specific compliance (CstL(S)/TLC25(S)) and the hysteresis ratio (HR) were measured in degassed lungs from normal adult (U) and young hamsters (Y), normal lungs with a ligated left main bronchus (L), and lungs from hamsters with elastase-induced emphysema (E) and bleomycin-induced interstitial fibrosis (B). HR was defined as the area enclosed within the inflation and deflation limbs of the volume-pressure curve, expressed as a percentage of the rectangle enclosing the curve. Lung disease index, a stereologic estimate of the extent of lung disease, was determined from histologic sections of the B group specimens. L group had significantly diminished CstL(S), TLC25(S) and CstL(S)/TLC25(S) values, but normal HR. Y group had decreased CstL(S) and TLC25(S) but normal CstL(S)/TLC25(S) and elevated HR. E group had increased CstL(S), TLC25(S), CstL(S)/TLC25(S) and HR. B group indexes were similar to those of the L group with diminished CstL(S) and TLC25(S), compared to the U group, but normal mean HR. B group was subdivided into normal and elevated HR groups; CstL(S) and CstL(S)/TLC25(S) were similar for the 2 groups, but the disease index was greater in the animals with elevated HR. Comparability of HR in the U and L groups indicated that HR is independent of lung size. Elevated HR in the Y group indicated that the viscoplastoelastic properties of young lung tissues are different from adult tissues. Mildly elevated HR of the E group may have been due to altered properties of the elastic fiber network. All B group animals had some loss of lung volume; only in the most extensively diseased lungs were altered viscoplastoelastic properties found. HR may be viewed as a measure of the viscoplastoelastic properties of pulmonary tissues. It is useful in assessing their functional integrity.