Tracheal Stenting for Tracheal Collapse
Tracheal collapse is a progressive, degenerative disease of the cartilage rings in which hypocellularity and decreased glycosaminoglycan content leads to dynamic tracheal collapse during respiration. This is a condition of predominantly middle-age, small and toy-breed dogs which can present with signs ranging from a mild, intermittent “honking” cough to severe respiratory distress from dynamic upper-airway obstruction. Many of these animals are palliated with medications including anti-inflammatories, cough suppressants, and bronchodilators. Candidates for surgical therapy are those that have failed initial conservative medical management.
Various surgical techniques have been described however the currently recommended surgical therapy is extraluminal polypropylene prostheses. This technique involves placing extraluminal support rings around the trachea during an open cervical approach and has a reported 75%-85% overall success rate in 90 dogs for reducing clinical signs.15 This procedure is not without complications however. The same study reported that 5% of animals died peri-operatively, 11% developed laryngeal paralysis from the surgery, 19% required permanent tracheostomies, and ~23% die of respiratory problems with a median survival of 25 months. More importantly, only 11% of the dogs in this study had intra-thoracic tracheal collapse (all dogs had extrathoracic tracheal collapse). The authors advised against this technique in animals with intra-thoracic tracheal collapse as the associated morbidity was unacceptably high.
Due to the relatively high morbidity associated with surgery, the use of intra-luminal stents has been investigated. A number of stents have been evaluated in the canine trachea, including both balloon-expandable (Palmaz), and self-expanding (Stainless steel, Laser-cut nitinol, Knitted nitinol) stents. Clinical improvement rates in 75%-90% of animals treated with self-expanding, intra-luminal stainless steel stents have been reported.16,17 Immediate complications were mostly minor although there was a peri-operative mortality rate of approximately 10%. Late complications included stent shortening, excessive granulation tissue, progressive tracheal collapse, and stent fracture.
The advantages of intra-luminal tracheal stenting include minimal invasiveness, avoiding dissection around the peri-tracheal neurovascular structures, shorter anesthesia times, and access to the entire intra-thoracic trachea. While most commonly performed under fluoroscopic guidance, some are now placing tracheal stents under endoscopic guidance. The search for a better intra-luminal tracheal stent continues and long-term studies will be necessary to determine late effects of these stents on the trachea and whether the progression of the tracheal collapse syndrome can be prevented or delayed through earlier intervention.