The nebulized papain produced histologically confirmed emphysema. Total lung capacity (TLC), RV, and RV/TLC increased in all animals. Lung compliance increased as well. After intubation and ventilation with 100% oxygen, selected lung subsegments were lavaged with “antisurfactant” solution via a multichannel, balloon-tipped catheter inserted through a fiberoptic bronchoscope. Following suction, a fibrin-based sealant was injected into the selected subsegment with bronchoscopic confirmation of effective sealing. Animals treated with this method of bron-choscopic volume reduction had significant reductions in TLC (64% return to baseline) and RV (72% return to baseline), with decreased compliance. Visual atelectasis was apparent at autopsy. These results were similar to those in a group of sheep treated with surgical lung volume reduction. Sterile lung abscesses developed in two of four of the sheep treated with bronchoscopic volume reduction. Only 11 of 20 subsegments treated exhibited sustained collapse. Reading here
A newer technique of bronchoscopic lung volume reduction has been recently reported by Ingenito et al. Six sheep in this study had papain-induced emphysema that produced increases in TLC, functional residual capacity (FRC), RV, and airway resistance with reduction in elastic recoil and Dlco. Six lung segments in each sheep had fiberoptic bronchoscopy with instillation of an enzymatic solution of trypsin to remove epithelial cells in the targeted region. This was followed by instillation of fibrin hydrogel and thrombin through a bronchoscopically placed catheter to promote fibroblast attachment and collagen synthesis. The intent was to remodel hyperinflated emphysematous lung segments into contracted scar tissue.
The bronchoscopic lung volume reduction procedure was well tolerated without hypoxemia or bron-chospasm. Three weeks after bronchoscopic volume reduction, there were significant reductions in TLC (3.63 to 3.01 L, p = 0.02), FRC (2.04 to 1.66 L, p = 0.05), and RV (1.43 to 0.63 L, p = 0.002). Recoil pressure increased. These improvements in lung function were maintained at 9 weeks. Dlco improved following bronchoscopic volume reduction, but not back to levels measured before papain installation. Serial CT scans and autopsy at 9 weeks after bronchoscopic lung volume reduction confirmed volume reduction and fibroblastic scar formation with collagen deposition in the treated areas. There were no lung abscesses with this method.