EVALUATION OF THE PALMAZ STENT IN THE TRACHEA AND MAINSTEM BRONCHI OFNORMAL DOGS

Objective- This study evaluates the efficacy of the Palmaz balloon exp andable intraluminal stent in the trachea and mainstem bronchi of norm al dogs. Study Design- Effects of the stent were evaluated by physical examination, thoracic radiography, respiratory tract fluoroscopy and endoscopy, tracheal diameter measurement, postmortem examination, and airway histomorphometry. Animals or Sample Population- Ten normal beag le dogs. Methods- Stent size was estimated from thoracic radiographs i n awake dogs. Group I dogs (n = 4) had two stents placed: one in the t horacic trachea (TT) plus a randomly chosen mainstem bronchus (MB). Gr oup II dogs (n = 3) had stents placed in the MB (one stent), TT (one s tent), and mid- or proximal cervical trachea (CT) (one or two stents). Three dogs were used as sham-operated controls (group III). Temperatu re, pulse, respiration, and cough were measured twice daily. Dogs were evaluated at 21 and 49 to 56 days after stent placement, euthanatized , and tissues were collected for histomorphometric analysis of stent i ntegration and epithelial pathology. Results- Mean tracheal diameters of awake (10.5 +/- 1.7 mm) and anesthetized dogs before stent implanta tion (13.9 +/- 2.0 mm) were significantly different (P < .01). Complic ations associated with stent placement included acute pulmonary edema (n = 2), stent migration (n = 7), stent collapse (n = 4 CT, 2 TT, and 1 MB), and positive tracheal culture (n = 10). Group II dogs coughed m ore at rest, exercise, and with tracheal palpation than dogs in other groups (P < .01). Group I dogs coughed more at rest than group III dog s (P < .01). Stent integration ranged from 0 to 91.3%. Squamous metapl asia and epithelial ulceration associated with stents ranged from 0 to 57.5% and 0 to 32.7%, respectively. Conclusions- Determination of ste nt size should be based on measurements taken on anesthetized dogs bec ause use of inappropriately sized stents may promote stent migration, squamous metaplasia, and/or ulceration. Epithelialization over stent s truts may occur if the stent is closely associated with tracheal epith elium. Clinical Relevance- Palmaz stents do not appear to be appropria te for placement in the CT of dogs; however, with technical modificati ons, application in the TT and MB may be feasible. (C) Copyright 1997 by The American College of Veterinary Surgeons.