The trachea, or windpipe, is a muscular tube that carries air from your dog’s nose and mouth to his lungs. Rings of cartilage hold the trachea open. If these rings become weakened, the trachea can collapse under the force of the air being inhaled or exhaled from the lungs. This condition is most prevalent in toy breeds.

Symptoms of a collapsing trachea are coughing, especially a honking cough, or difficulty breathing, particularly after exercise.

The reason that the cartilage rings weaken and collapse is unknown, but a hereditary cause is suspected.