A Retrievable Nitinol Endobronchial Stent: An Experimental Study in Dog

PURPOSE: The purpose of this study was to evaluate the safety and the retrievability of a new coveredretrievable nitinol tracheobronchial stent. MATERIALS AND METHODS: Stents were knitted from 0.2mm nitinol wire,covered with polyurethane, and were 20 -22mm in diameter and 2cm in length. Under fluoroscopic guidance, a stentwas placed in the normal right bronchus intermedius of ten dogs. Using a retrieval hook, stent retrieval wasattempted after 1 month(N=5) or 2 months(N=5). After removal, the dogs were sacrificed and their tracheobronchialtrees were examined grossly and histologically. RESULTS: Eleven stents were successfully placed in ten dogs.Migration and expectoration occurred in four of ten stents in nine dogs(40%). Five stents were successfullyremoved from six dogs(83%). Without significant difference between the two groups, mild to moderate mucosalhyperplasia was noted at the sites of stents as well as above and below them. On microscopy, three of five dogsshowed pneumonia in the right middle lobes, but none of the stents was covered with epithelium. CONCLUSION:Temporary placement of a covered expandable nitinol stent in the tracheobronchial tree is feasible, but toestablish its efficacy, further experimental studies are needed.