A flat or dull sound on chest percussion indicates which of the following?

• A. Fluid or solid.
• B. Normal sound.
• C. Air in pleural space.
• D. Hyperresonant sound.

Answer: (A)

Percussion notes reflect what's beneath the chest wall. A flat or dull sound means there’s increased density—fluid or solid tissue—underneath. That’s why this finding points to fluid in the pleural space or a solid lesion/consolidation in the lung. Normal lung is resonant, so it wouldn’t be dull. A pneumothorax or excess air in the chest makes percussion more tympanic or hyperresonant, not dull. So the flat/dull percussion best indicates fluid or solid underlying material.