A 3-year-old boy presents with acute onset of cough and wheezing. Focal wheezing is heard in the right lower lung. Which test should be ordered to confirm the suspected diagnosis?

A 3-year-old boy presents with acute onset of cough and wheezing. Focal wheezing is heard in the right lower lung. Which test should be ordered to confirm the suspected diagnosis?

• A. Arterial blood gas
• B. Inspiratory and forced expiratory chest x-rays
• C. PA and lateral chest x-ray
• D. Peak expiratory flow rate

Answer: (B)

In a young child with sudden coughing and a localized wheeze, foreign body aspiration is a key possibility, and the most informative way to confirm it is to use chest imaging in both inspiration and expiration. The expiratory view is especially helpful because a partial airway obstruction allows air to escape during inspiration but traps air during expiration, producing unilateral hyperinflation on the affected side. This air-trapping sign can reveal an obstruction even when the foreign body itself isn’t visible on the radiograph, making inspiratory and expiratory films more sensitive than a single static view. Arterial blood gas won’t confirm the diagnosis; it may show hypoxemia or respiratory distress but doesn’t localize obstruction. A PA and lateral chest x-ray provide a standard snapshot and can miss subtle air trapping. Peak expiratory flow rate isn’t practical or reliable in a 3-year-old and doesn’t diagnose the cause of wheeze in this scenario.

In a young child with sudden coughing and a localized wheeze, foreign body aspiration is a key possibility, and the most informative way to confirm it is to use chest imaging in both inspiration and expiration. The expiratory view is especially helpful because a partial airway obstruction allows air to escape during inspiration but traps air during expiration, producing unilateral hyperinflation on the affected side. This air-trapping sign can reveal an obstruction even when the foreign body itself isn’t visible on the radiograph, making inspiratory and expiratory films more sensitive than a single static view.

Arterial blood gas won’t confirm the diagnosis; it may show hypoxemia or respiratory distress but doesn’t localize obstruction. A PA and lateral chest x-ray provide a standard snapshot and can miss subtle air trapping. Peak expiratory flow rate isn’t practical or reliable in a 3-year-old and doesn’t diagnose the cause of wheeze in this scenario.