Clinical and histologic evaluation of an indwelling, inflatable, long-term laryngeal stent in the canine model

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Objective: The goal was assessment of a revolutionary approach to laryngeal stenting. A radically designed, atraumatic, inflatable, low-pressure, high-volume, endoscopically inserted laryngeal stent for effective intralaryngeal support or long-term prevention of aspiration was prospectively evaluated in a canine model to reveal any significant short- and long-term anatomic and functional changes in the larynx. Methods: A self-sustaining, tube-free, long-term flap tracheostomy was performed in 14 dogs, followed by endoscopic laryngeal stent insertion. The stents were inflated, and their intraluminal pressures were monitored daily. The stenting period ranged between 3 and 46 days (mean 27.4 days). The animals were then euthanized, and total laryngectomy was performed. The larynges underwent gross and microscopic examinations, and a grading scale of reactive changes caused by the stent placement was created on the basis of the findings. Results: Dye studies for aspiration were negative in all animals. Gross findings consisted of varying degrees of small ulceration, localized polypoid lesions, and granulomas. Grossly, 9 dogs exhibited small superficial ulceration of the true vocal cords and posterior commissure. Six dogs developed minor polyps or polypoid changes and/or granulomas, respectively. No gross changes were seen in 2 of the dogs. Histopathologically, 10 dogs demonstrated grade I or II histopathologic changes. Only 4 of the dogs exhibited inflammation extending into the underlying cartilages, grade III. One dog did not complete the observation period. Conclusion: This new stent demonstrated safety and biocompatibility with minimal local tissue reaction to its extended long-term placement. Good tolerance to the stent was documented, with minimal side effects similar to those that would be observed in human subjects after endotracheal intubation. When followed up in human patients, such minimal lesions have not resulted in significant long-lasting functional impairments. These initial results would indicate that this stent is well tolerated for long-term application and qualify as the preferred device for both management of aspiration and postoperative endolaryngeal bolstering support. (Otolaryngol Head Neck Surg 1999;121:195-202.)