Respiratory work in elastase treated hamsters.

Biomechanical adaptations of the diaphragm in the hamster model of emphysema are similar to those observed in skeletal muscle with exercise training. The aim of this study was to evaluate whether the dynamic pressure-volume (PV) work of breathing in hamsters with elastase-induced emphysema may contribute to these adaptations. PV work in elastase treated animals was compared to healthy controls. The studies were performed in adult hamsters 14-16 months following intratracheal administration of elastase (elastase treated group, ET) or saline (control group, CTL). Airway and esophageal pressures and air flows were measured during spontaneous breathing in anesthetized, supine animals. Pulmonary work (WL) was computed from transpulmonary pressures and airflows. Functional residual capacity (FRC) and total lung capacity (TLC; defined as volume at 25 cmH2O) in ET were increased 2 and 1.8 times, respectively, compared with CTL. Averaged tidal volume (VT) and inspiratory flows were comparable between groups. Total work of breathing (WT) normalized per ml VT was not significantly affected with elastase treatment but the pulmonary elastance work (WE) was significantly less in ET animals than controls (0.88 +/- 0.61 g cm(-2) vs. 1.63 +/- 0.32). Pulmonary resistive work was not significantly different between ET and CTL animals. These results suggest that biomechanical adaptations of the diaphragm observed in ET hamsters are caused by mechanisms other than the changes in dynamic mechanical properties of the lung following elastase treatment.