The trachea, or windpipe, is the tube that delivers air from the mouth to the lungs and vice versa. It is surrounded by c-shaped rings of rigid cartilage that are spaced evenly down the entire length of the tube. The rings hold the tube open so that it cannot collapse into itself like a straw in a milkshake. Toy breeds of dogs may inherit a weakness in the rings which make them susceptible to a collapsed trachea.
The trachea is not meant to change shape during respiration. In a dog with a collapsed trachea however, it may collapse in the upper (cervical) portion of the trachea with inspiration or the lower (intra-thoracic) portion with expiration. This effect causes the sensation that something is lodged in the throat, and a chronic cough develops. The trauma to the trachea during constant coughing increases mucoid secretions that further obstruct the airway. The disease becomes progressive. Chronic oxygen starvation can then lead to heart failure and other secondary consequences.
Factors that exacerbate symptoms of a collapsed trachea are heat and humidity, obesity, heart failure (which can be secondary to collapsed trachea), inhalant allergens like cigarette smoke, respiratory infection, and anxiety. These can increase the coughing and tracheal deformation to the point of suffocation. The dog may pass out from anoxia – lack of oxygen to the brain. In fact, dogs with collapsed trachea may have elevated liver enzyme tests from chronic oxygen deprivation.
Breed predilection and x-rays confirm a diagnosis of a collapsed trachea, and treatment begins with cough suppressants and bronchodilators. Secondary heart failure will be treated with specific drugs, although the health of the heart may improve by controlling the airway disease. A weight loss program should be started for obese dogs. Avoidance of irritants like smoke is very important. As the disease progresses, surgery may be an option. Not all collapsed tracheas can be repaired however. If the weakness in the cartilaginous rings is in the throat, synthetic rings can be sutured in place. If the defect is in the chest, surgery may not be corrective or even possible. Many dogs with a collapsed trachea have a weakness in the walls of the bronchi, the main branches of airway into the lungs. For these pets, symptomatic treatment is the only option.
Because a collapsed trachea is heritable, affected dogs should not be bred.