Tracheal Collapse: Diagnosis and Treatment
Carly Waugh, DVM, DACVIM
Tracheal collapse is a progressive disease of the cartilaginous rings within the trachea seen often in middle-aged, small-breed dogs. This is most commonly found in Yorkshire terriers, Pomeranians, pugs, Chihuahuas and toy poodles and results in dorsoventral narrowing of the tracheal lumen. The cause is unknown, but a strong genetic predisposition is suspected. Tracheal collapse should be suspected when dogs have a “goose honk” cough, noisy breathing and periodic dyspnea. Coughing episodes are worsened with excitement, anxiety and pressure on the trachea and can result in respiratory distress in severely affected dogs. As the condition progresses, the degree of collapse worsens, causing the cartilaginous rings to become more ovoid. This increases the cough severity and causes exercise intolerance. Severe tracheal collapse can also result in pulmonary hypertension and right-sided heart disease.
Definitive diagnosis and characterization of tracheal collapse is based on a combination of thoracic and cervical radiographs, fluoroscopy and tracheobronchoscopy. Collapse of the cervical trachea is best seen during inspiration, and intrathoracic collapse is seen best during exhalation on radiographs. With tracheobronchoscopy, tracheal collapse severity can be graded from grade I to IV (25-100% collapse). Laryngeal function and main stem bronchial collapse can also be assessed. Samples are often obtained for culture and cytology.
Medical management of tracheal collapse is the most important aspect of treatment, particularly when signs of collapse are first noted. Weight loss, limiting exposure to irritants (dust, cigarette smoke) and utilizing a harness rather than a collar are of paramount importance and can dramatically improve clinical signs. Oral antitussives (butorphanol, hydrocodone, diphenoxylate) are also important medications in helping to limit the clinical signs and progression of the disease. Tapering doses of corticosteroids (prednisone or inhaled fluticasone), bronchodilators (theophylline, terbutaline), and tranquilizers (acepromazine) are also used to treat affected patients. These patients are also predisposed to the development of bacterial tracheitis, necessitating antibiotic treatment if present.
When medical management is not successful in controlling clinical signs, more definitive treatment should be considered. Extraluminal placement of prosthetic rings can be performed, although this requires surgery. Recurrent laryngeal nerve damage can be a complication with this approach, and the blood supply to the trachea can be disrupted, causing tracheal necrosis.
Minimally invasive structural support of the trachea is now readily available, reducing risk of complications seen with extraluminal ring placement. Self-expanding nitinol stents can be placed, helping the trachea stay open by relying on the cylindrical shape of the stent. They are particularly advantageous due to the short post-operative recovery, rapid restoration of the airway and minimally invasive nature of placement. Measuring the tracheal diameter and length of stent can be challenging as the stents foreshorten during placement. Final stent width should be 10-20% larger than the maximal diameter of the trachea to prevent stent migration. The stent should be at least 1 cm caudal to the cricoid cartilage and 1 cm cranial to the carina and span the entire length of the collapse. Sizing is performed with the patient under general anesthesia with a measuring catheter in the esophagus, ideally with stent placement immediately following under the same anesthesia.
After stent placement, the patient is recovered and discharged with antitussives, sedatives, a tapering dose of corticosteroids and antibiotics. Aggressive control of the cough should be achieved for at least 4 weeks after stent placement in order to prevent stent fracture or granulation tissue formation. Radiographs are repeated at 1, 3 and 6 months post-placement. It should be noted that cough will persist after placement of the stent due to tracheal irritation, but improvement in quality of life should be noted quickly in appropriately selected patients.