Most commonly, tracheal collapse occurs in middle-aged to old dogs including Yorkshire terriers, Pugs, Chihuahuas, Pomeranians, Maltese, as well as Miniature and Toy Poodles.
Affected dogs might present with a variety of clinical signs ranging from coughing and exercise intolerance to episodes of cyanosis and collapse. The stress of a physical examination can exacerbate clinical signs.
Definitive diagnosis can best be obtained with the use of fluoroscopy while the patient is awake. Generally, the unsedated patient is held in lateral recumbency, and the cervical trachea is massaged to induce coughing. Using fluoroscopy, the location and extent of the collapse can be documented. Some veterinarians advocate the use of endoscopy in combination with fluoroscopy.
Endoscopy allows visualization of the internal surface of the larynx and trachea but might not accurately define the extent of the collapse. Another means of diagnosing this disease is radiography (Photo 1); however, radiography is not a dynamic diagnostic tool, and affected patients may be missed, or the extent of collapse may be underestimated. In fact, in one study, radiographs were normal in 20 percent of cases. Alternatively, a tentative diagnosis can be made and conservative treatment initiated based on signalment and clinical signs.
Photo 1: A lateral thoracic radiograph documenting tracheal narrowing extending from the mid-cervical area to the mainstem bronchi in a toy breed dog.
The pathophysiology of the collapsing trachea is not completely understood. It has been suggested that dorsoventral flattening of the c-shaped tracheal rings is secondary to decreased chondroitin sulfate and calcium and/or hypocellular cartilage.
Photo 2: The stent delivery system can be placed easily through an endotracheal tube. The metallic markers on the delivery system can be seen easily with fluoroscopy and aid in deployment.
The weakened tracheal cartilage predisposes the rings to collapse during the pressure changes of normal ventilation. Also, redundancy of the dorsal membrane may be a contributing factor.
Traditional therapy for collapsing trachea consists of medical management, including cough suppressants, anti-inflammatory medications, bronchodilators and tranquilizers. The main goals of medical management include depressing the cough, reducing tracheal inflammation and reducing excessive excitation. Cough suppressants, such as hydrocodone, lomotil and butorphanol, can be used as frequently as every six hours. The most common side effects of these medications include constipation, depression and lethargy. The anti-inflammatory medications most commonly used are corticosteroids, such as prednisone and dexamethasone. Steroids, such as fluticasone (Flovent) can be used as inhaled medication with the help of a pediatric spacer. Steroids are useful for treating tracheitis and laryngitis that occur secondary to coughing and tracheal collapse. The side effects of the corticosteroids can include polyuria, polydypsia, polyphagia and gastrointestinal irritation. These systemic effects are reduced when administered as inhaled medication. Bronchodilators are used to open the lower airways to increase gas exchange. Bronchodilators, such as theophylline and aminophylline, can also have an anti-inflammatory effect and can help reduce inflammation that occurs in the trachea. The side effects of bronchodilators might include vomiting, diarrhea, excitement and insomnia. Tranquilizers are often used to prevent excessive excitation. In most cases, we recommend only starting with a single drug, then adding additional therapies one at a time so that the patient's clinical response to each therapy can be evaluated.
Photo 3: Fluoroscopic view of the stent delivery system within the trachea prior to deployment.
When the clinical signs are not controllable by medical management alone, additional methods of therapy should be considered. Reported surgical options for collapsing trachea include plication of the dorsal tracheal membrane, placement of extraluminal polypropylene prosthetics and placement of intraluminal stents. With extraluminal techniques, spiral or c-shaped polypropylene prosthetics are sutured along the exterior of the extrathoracic collapsing portion of the trachea.
Complications include tracheal necrosis and laryngeal paralysis. In one study, 16 percent of patients had a permanent tracheostomy performed within two weeks of extraluminal c-shaped stent placement, and 6 percent died from complications associated with laryngeal paralysis in the immediate post-operative period. In addition, these extraluminal techniques are not recommended for intrathoracic tracheal collapse.