A 9-year-old 5-kg (11-lb) spayed female Shih Tzu crossbred dog was evaluated for a 2-day history of coughing and hacking that developed after the dog ate a rawhide chew. The owners reported that the dog's coughing seemed to occur after excitement and was progressive. The dog had no known history of trauma or being around other dogs.
On physical examination, the dog was alert and responsive, had a body condition score of 5 (on a scale of 1 to 9), and had a grade 2/6 heart murmur. The dog was tachypneic (56 breaths/min; reference range, 10 to 35 breaths/min),