A nurse is caring for a toddler who has acute laryngotracheobronchitis and has been placed in a cool mist tent. Which of the following findings indicates that the treatment has been effective?

The correct answer is C: Decreased stridor. Stridor is a high-pitched, noisy breathing sound that indicates upper airway obstruction, common in laryngotracheobronchitis. A decrease in stridor suggests improved airway patency due to reduced inflammation in the airway. Improved hydration (choice A) is important but does not directly indicate the effectiveness of the cool mist tent. Decreased temperature (choice B) may be a sign of reduced inflammation but is not specific to the airway. Barking cough (choice D) is a symptom of croup and may persist even with effective treatment.