PURPOSE: In previous studies, our group developed the HCPA-1 silicone stent for use in patients with tracheobronchial diseases. Established tracheal stenosis models were tested; technical difficulties, however, limited the assessment of desired variables. Thus, there was no satisfactory model that was both less invasive and safe. This study was aimed at creating a model of tracheal paralysis allowing assessment of biocompatibility of the HCPA-1 stent. Botulinum toxin-induced neuromuscular blockade after injection into the tracheal mucosa was used for stent stabilization in the trachea.
METHODS: The proposed experimental model was tested in felines (n=4) and swine (n=4). Groups A and B comprised one of each animal and Group C two of each. Group A (n=2) underwent stent implantation with submucosal saline injection into the trachea under bronchoscopic view. Group B (n=2) received botulinum toxin in equal volumes as sole intervention. Group C (n=4) received botulinum toxin and underwent stent implantation. They were monitored by periodical X-ray, bronchoscopy and esophageal manometry examinations. Then animals underwent euthanasia in six weeks. Tracheal stumps were submitted to histopathologic examination. A score was applied for counting the ensuing changes: inflammatory cells, erosions, depth of changes in the tracheal wall and granulomas. The study was approved by the institution's Commission on Ethics and Research, with attention to humane treatment of animals.
RESULTS: Slight tracheal dilatation ocurred in animals that received botulinum toxin. In Group A, the feline that did not receive botulinum toxin expelled the stent in the first week after implantation. Groups A and B showed mild inflammatory submucosal infiltrate. Group C suffered moderate caudal migration of the stents and showed moderate infiltrate with scattered granulomas. However, there was no significant tracheal damage in any of the animals.
CONCLUSION: Botulinum toxin seems to be effective in preventing expulsion of the silicone stents. This model allows assessment of the tracheal wall in contact with the stents.
CLINICAL IMPLICATIONS: This study provides a mini-invasive animal model for testing new tracheobronchial stents.
DISCLOSURE: Rogerio Xavier, No Financial Disclosure Information; No Product/Research Disclosure Information