Tracheobronchial metal stents: Effects of covering a bronchial ostium in pigs

Rationale and Objectives. The purpose of this study was to examine the effe cts of placing a metal stent across a bronchial orifice. Materials and Methods. Nine pigs were used as test subjects, because the ri ght upper lobe bronchus comes directly off the trachea in these animals. On e of three types of metal stents was placed into the trachea of each pig an d covered the orifice of the right upper lobe bronchus. Follow-up studies w ere performed at 1 and 3 months to evaluate the right upper lobe for signs of bronchial obstruction. infection, and atelectasis. The animals were sacr ificed at 3 months to study the histopathologic changes of the trachea and lungs. Results. Two upper lobe bronchi remained patent, seven were obstructed by g ranulation tissue or plugs of mucus and inflammatory cells. Right upper lob e infiltration and atelectasis were seen in eight animals. Interestingly, r adiographic opacities were also common in other lung segments. There was a tendency toward fewer and less extensive lung opacities at 3 months compare d with that at 1 month. At histopathologic examination, areas of both acute and chronic pneumonia were found in the right upper lobe of all animals. T he segment of trachea covered by the stent was lined with a thin layer of g ranulation tissue containing neutrophils. monocytes. and lymphocytes. The s tent luminal surface was covered with columnar, cuboidal. and stratified sq uamous epithelium. Tracheal stenosis was seen in three animals because of e xcessive granulation tissue in two and a collapsed stent in one. Conclusion. Placement of metal stents in pig trachea covering the orifice o f the right upper lobe bronchus resulted in retention of secretions and sec ondary infection in the right upper lobe and other distant lung segments.