Certified Respiratory Therapist Practice Exam

The characteristic that would be seen on a chest radiograph for a child diagnosed with croup is the steeple sign, which indicates subglottic edema. Croup, commonly caused by viral infections, leads to inflammation and narrowing of the airway, particularly in the subglottic area. The steeple sign is described as a tapering of the airway in the cervical region, resembling the shape of a church steeple, and can often be visualized on an anteroposterior (AP) view of the neck or chest radiograph. In this context, while normal lung fields may be observed in a child with croup, they do not signify the condition itself and are not diagnostic features. Similarly, pleural effusion is not typically associated with croup, and an enlarged thymus gland is not relevant in this case, as it pertains more to different conditions and age groups. Therefore, identifying the steeple sign is critical in confirming the diagnosis of croup, making it the correct answer in this scenario.