- Signalment: 12-year-old female spayed Yorkshire terrier (4.1 kgs)
- Presenting complaint: Progressively worsening periods of inspiratory dyspnea with mild coughing
- Pertinent history: 3-year history of collapsing trachea and mild chronic valvular disease; Failed medical management with Theophylline ER, Butorphanol, Diphenhydramine, Enrofloxacin, and/or Acepromazine
- Medications: Prescription diet w/d (Hill’s Pet Nutrition), Hydrocodone (2.5mg orally very 6 hours), Prednisone (2.5mg orally every 12 hours)
- Physical examination findings: Bright, alert, and responsive; body condition score 6/9; Grade 2/6 holosystolic heart murmur, intermittent inspiratory dyspnea with mild cyanosis, inducible cough upon tracheal palpation, profound increased inspiratory respiratory effort (suggesting upper airway involvement) with moderately increased expiratory effort as well (suggesting intrathoracic tracheal and/or bronchial involvement)
- Hemoglobin Saturation: 94%
- Complete blood count: Mils stress leukogram
- Serum chemistry profile: ALT 79, AST 39, ALP 420
- Thoracic and cervical radiographic and fluoroscopic examination: (See Figure 1)
- Cardiology Consult: Mild chronic valvular disease
Figure 1: Lateral thoracic and cervical static fluoroscopic image demonstrating cervical and thoracic inlet tracheal narrowing (black arrows) and open intrathoracic tracheal lumen and carina (white arrows).
This patient had received various medications with little improvement in clinical signs. Historical cardiology consultation reported no need for cardiac medications needed at that time. Presentation 2 weeks earlier resulted in final attempt at medical management including antibiotics, steroids, and anti-tussives. No major improvement in clinical signs led to consideration for more aggressive interventions. Discussion with the owner included extraluminal tracheal ring placement and intraluminal stent placement. While the primarily inspiratory clinical signs suggested more severe extrathoracic tracheal collapse, physical examination and fluoroscopic evaluation suggested concurrent intrathoracic tracheal and bronchial collapse. Tracheal stenting was chosen to treat both the extrathoracic and intrathoracic tracheal collapse. Under general anesthesia and using fluoroscopic guidance, positive pressure (Figure 2; 20cm H2O) and negative pressure (Figure 3; -15cm H2O) ventilation tracheal measurements were made in order to determine the maximal tracheal diameter and determine the extent of the tracheal and/or bronchial collapse. A self-expanding metallic tracheal stent was placed through the endotracheal tube (Figure 4) and the patient was recovered in 40% oxygen in the ICU and until awake and ambulatory.
Figure 2: Lateral thoracic and cervical static fluoroscopic image obtained at 20cm H2O positive pressure ventilation (PPV) demonstrating maximal tracheal diameter. A marker catheter (black arrows) is in place in the esophagus for measurement purposes. The carina is open (white block arrow). Line 3 is 10mm and used to calibrate the image in order to determine the diameter of the trachea (Line 4).
Figure 3: Lateral thoracic and cervical static fluoroscopic image obtained at -15cm H2O negative pressure ventilation (NPV) demonstrating diffuse tracheal collapse (black arrows) as well as carina and mainstem bronchial collapse (white block arrow) not previously apparent without NPV.
Figure 4: Lateral thoracic and cervical static fluoroscopic image immediately following intraluminal stent placement demonstrating re-established tracheal lumen patency (white arrows).
This patient was discharged from the hospital the following day with resolution of the dyspnea. A mild dry cough persisted. Discharge medications included a 3-week tapering dose of corticosteroids (prednisone 2.5mg orally twice daily to start), hydrocodone (2.5mg orally every 6 hours), and a 10-day course of enrofloxacin (40mg compounded orally once daily). Follow-up phone calls each week confirmed she continued to do well. Recheck examination 4 weeks later showed dramatically improved respiration with progressive resolution of the dry cough. Occasional periods of excitement-induced coughing episodes continued but dramatically improved compared to pre-stent episodes. Re-examination at 3 months, 6 months, and 1 year demonstrated similar clinical signs; Every other day prednisone remained necessary as well as daily hydrocodone therapy.
Tracheal collapse is a progressive, degenerative disease of the cartilage rings in which hypocellularity and decreased glycosaminoglycan content lead to dynamic tracheal collapse during respiration. More recently, tracheal ring malformations have been found to also contribute to tracheal lumen obstruction and respiratory compromise. Tracheal collapse is a condition of predominantly middle-age, small and toy-breed dogs that develop a wide and varying range of symptoms varying from a mild, intermittent “honking” cough to severe respiratory distress from dynamic upper-airway obstruction. Many of these patients (like the example above) are successfully palliated for years with conservative treatments (weight loss, management of comorbidities, etc.) and medications including anti-inflammatories, cough suppressants, and bronchodilators. Once medical management fails to provide an acceptable quality of life, more aggressive interventions are considered.
The two most commonly performed treatment options include extraluminal tracheal rings and intraluminal tracheal stenting. Tracheal ring surgery 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.1 This procedure is limited to those patients with collapse limited to the cervical trachea (primarily inspiratory dyspnea) and is not without complications. 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 advantages of intraluminal self-expanding metallic stent (SEMS) placement include minimal invasiveness, shorter anesthesia times, and access to the entire cervical and intrathoracic trachea. Disadvantages include misplacement, choosing the inappropriate stent size, and an unknown but relatively low risk of stent fracture. Two studies report clinical improvement rates in 75%-90% of animals treated with intra-luminal SEMS.2,3 Immediate complications were typically minor although there was a reported peri-operative mortality rate of approximately 10%, a rather high figure compared to the author’s experience. Late complications included stent shortening, excessive granulation tissue, progressive tracheal collapse, and stent fracture. Complications are often due to inappropriate stent placement or sizing which is reduced with experience.
For stent placement, the patient is placed under general anesthesia, tracheal measurements are made, and an appropriately sized stent is placed through an endotracheal tube and deployed during direct visualization using fluoroscopy. The stenting procedure is fairly short and the patients are typically discharged from the hospital the following day. Medical management with corticosteroids and anti-tussives continues initially and most dogs will need continued anti-tussive medications for life. Those with concurrent low-airway disease will often benefit from continued corticosteroid therapy as well.
Submitted by Dr. Chick Weisse
1 Buback JL, Boothe HW, and Hobson HP. Surgical treatment of tracheal collapse in dogs: 90 cases (1983-1993) Journal of the American Veterinary Medical Association 1996; 208(3):380-384.
2 Norris JL, Boulay JP, Beck KA, et al. Intraluminal self-expanding stent placement for the treatment of tracheal collapse in dogs (abstr), in Proceedings, 10th Annual Meeting of the American College of Veterinary Surgeons 2000.
3 Moritz A, Schneider M, and Bauer N. Management of advanced tracheal collapse in dogs using intraluminal self-expanding biliary wallstents. Journal of Veterinary Internal Medicine 2004; 18:31-42.