MMP9 and Tracheomalacia: The main stent-related complications were granulation hyperplasia, scar contracture, stent migration, secretion retention, tracheomalacia after implantation every 2 week First, we selected the multiple inflammatory factors were detected the tracheal mucosa of rabbits after stent implantation by protein microarray, then the expression levels of IL-1RA, IL-8 and MMP9 were determined by ElISA to understand the mechanism of stent complications.