If inspiratory radiographs are normal but suspicion remains, which projection helps detect air trapping?

If inspiratory radiographs are normal but suspicion remains, which projection helps detect air trapping?

• A. Expiratory radiographs
• B. Lateral view
• C. CT scan
• D. Upright chest radiograph

Answer: (A)

Air trapping is best seen on expiratory imaging because it reveals regions that do not empty properly when you breathe out. On an expiratory radiograph, normal lung areas deflate and become relatively denser, while areas with partial airway obstruction hold onto air and stay more inflated. That difference makes trapped air conspicuous, even when inspiratory views look normal. The other options aren’t as specific: a CT scan can detect air trapping but isn’t a projection, and an upright chest radiograph can show generalized hyperinflation but isn’t as sensitive for subtle trapping as an expiratory film. The lateral view doesn’t provide the same dynamic expiratory comparison that highlights trapped air.

Air trapping is best seen on expiratory imaging because it reveals regions that do not empty properly when you breathe out. On an expiratory radiograph, normal lung areas deflate and become relatively denser, while areas with partial airway obstruction hold onto air and stay more inflated. That difference makes trapped air conspicuous, even when inspiratory views look normal. The other options aren’t as specific: a CT scan can detect air trapping but isn’t a projection, and an upright chest radiograph can show generalized hyperinflation but isn’t as sensitive for subtle trapping as an expiratory film. The lateral view doesn’t provide the same dynamic expiratory comparison that highlights trapped air.