Tracheal collapse is a common cause of airway obstruction in dogs. The condition was first described in dogs in 1941. The trachea (windpipe) is normally a rigid circular tube. Typically, if the trachea collapses, it is compressed from top to bottom, as opposed to side-to-side. The section that collapses is usually the part of the trachea that enters the chest, but it can occur anywhere, from the throat all the way down to the first part of the lungs.

Tracheal collapse is mainly a disease of toy-breed dogs of either sex. Yorkshire terriers are most commonly affected, but Pomeranians, Chihuahuas, poodles, Maltese and pugs are also predisposed. Any age dog can be affected, but the average age at which clinical signs first occur is usually six or seven years.

Dogs are brought to the veterinarian with a history of coughing for several weeks or months, although, less commonly, it may present as a sudden episode. Other possible presenting signs are intolerance to exercise, labored breathing and cyanosis (bluish tinge to the gums). Excitement, eating, drinking, irritants like smoke or dust, obesity, excitement and hot or humid weather may provoke a coughing spasm.

The cause of the collapse is unknown, but there are probably several factors at play. Abnormal synthesis of the components that make up the cartilage found in the trachea is believed to be the cause of tracheal weakness. The weakened trachea flattens from top to bottom, obstructing the flow of air in and out of the lungs.

There are other possible causes of tracheal collapse, such as congenital defects, chronic airway disease, trauma and tumors that compress the trachea from the outside. There are other conditions that can cause coughing, and this can exacerbate the collapse of the trachea. For example:

Extra-long soft palate

Obesity

Chronic bronchitis

Pneumonia

Congestive heart failure

Respiratory irritants such as smoke or excessive dust

Allergic bronchitis

Once collapse has occurred, coughing will perpetuate further coughing by causing irritation and inflammation of the trachea. The irritated trachea will produce mucus and other secretions that further obstruct the airway. Medical treatment is undertaken to try to break the cycle of coughing, inflammation and excessive mucus production. If medical therapy fails, surgical therapy may be attempted.