Respiratory mechanics in hamsters following treatment with endotracrael elastase or collagenase

Abstract

Using a water-filled esophageal catheter and a body plethysmograph, static respiratory mechanics were measured in anesthetized hamsters 18-21 days following endotracheal treatment with elastase or collagenase. In elastase-treated hamsters, the functional residual capacity (FRC), volume of air in the lungs at transpulmonary pressure (PL) -20 cmH2O (RV[residual volume]-20), and at PL 25 cmH2O (TLC[total lung capacity]25), were all increased. The quasi-static compliance (Cst(L)) was also increased but chord compliance between PL 15-25 cmH2O (Cst(L)15-25) remained unchanged from control. In collagenase-treated hamsters, all values were unchanged from control except for increases in Cst(L)15-25 and TLC25. The increases in TLC25 and Cst(L)15-25 were greater in hamsters treated with 2 doses of collagenase than with a single dose. Similar changes were shown in the volume-pressure curves of saline-filled lungs. The alveolar architecture of the collagenase-treated lungs was normal, but elastase-treated lungs showed widespread panacinar emphysema. Destruction of elastic fibers appears to be necessary to produce the anatomical and physiological changes of experimental emphysema. These data support the concept that collagen fibers are the major determinant of the upper flat portion of the volume-pressure curve of the normal lung.