An acute infection causing lower airway obstruction: which initial symptom is expected?

• A. Wheezing
• B. Atelectasis
• C. Over-inflation
• D. Barrel chest

Answer: (A)

Wheezing is the best answer because an acute infection that causes lower airway obstruction, such as bronchiolitis, narrows the small airways and creates turbulent flow during exhalation. That turbulent flow produces a musical, high-pitched sound heard with auscultation—wheezing—the earliest sign of obstructed airways in infants. Other findings like hyperinflation or over-inflation on imaging reflect later or sequential changes from air trapping, while atelectasis can occur with mucus plugging but isn’t the initial symptom. Barrel chest points to long-standing or more chronic changes, not the immediate acute presentation.