The cartilaginous rings of the windpipe, or the trachea, are shaped like the letter C lying on its back. A small membrane covers the top of the ring. In many small breeds of dogs, the tracheal cartilage loses its rigidity if the membrane stretches. The rings can collapse and the windpipe flattens, causing mild to severe obstruction of the trachea. Common breeds affected are the miniature poodle, Pomeranian, Yorkshire terrier and Chihuahua. Some dogs can start showing signs of tracheal collapse at a relatively young age, but it is usually a disease of older dogs. The cause is not well understood; the proposed series include genetic factors and degeneration of the tracheal cartilages.
Major clinical signs are abnormal respiratory noises, difficult breathing, exercise intolerance and a harsh, dry cough. This is usually an intermittent goose-honking cough that has a sudden onset, especially when the dog is stressed. Applying pressure to the trachea or windpipe often induces this cough. Chest X-rays demonstrate tracheal collapse and affected dogs. The definitive diagnostic method is endoscopy, which involves passage of a scope into the trachea and viewing the collapse. Endoscopy also allows collection of samples of the trachea for bacterial culture, as many dogs have secondary infections.
Treatment of tracheal collapse is almost always done with medical therapy. This is usually effective in dogs with mild collapse and clinical signs. This medical therapy involves cough suppressants, drugs to dilate the trachea and bronchi as well as antibiotics for secondary infections. Anti-inflammatory steroid medications may be used on a short-term basis to reduce inflammation of the lining of the trachea. Some dogs benefit from the use of tranquilizers during periods of excitement. The owners are advised to minimize excitement with their dogs and high environmental temperatures. Obese dogs are placed on a weight-reduction diet.
Because of the inherent risks and potential complications related to tracheal surgery, most of these cases are managed medically whenever possible. Surgery is reserved for dogs with severe collapse and little or no response to medical therapy.
Tracheal collapse is commonly a progressive disease, and surgery of the trachea is fraught with many complications. Talk to your veterinarian if you have a small-breed dog that has a chronic cough, especially one that is made worse with exercise or excitement.
Dr. Karsten Fostvedt is a veterinarian at St. Francis Pet Clinic in Ketchum.