Review Question - QID 213447

A 3-year-old boy is brought to the emergency room by his parents due to noisy, difficult breathing. They are concerned that he may have swallowed something when they were not looking. The parents note that he has had a fever and runny nose for the past few days. On physical exam, the patient has a cough and exhibits breathing with inspiratory stridor. A chest radiograph is obtained and shows the finding seen in Figure A. The physician explains that no treatment is needed, though nebulized epinephrine may be used to alleviate symptoms. What is the most likely cause of this patient’s difficulty breathing?