What can dull sounds during percussion over the lungs indicate?

Dull sounds during percussion over the lungs typically indicate the presence of fluid or solid mass in the lungs or pleural space. This is because dullness replaces the normal resonance of healthy lung tissue due to conditions that increase density in the area being assessed.

In the case of pleural effusion, fluid accumulation in the pleural space alters the normal air-filled lung sound to a dull sound. Similarly, pneumonia may cause consolidation—where lung tissue becomes filled with fluid or pus—resulting in a similar dull tone upon percussion. The involvement of either pleural effusion or pneumonia explains why this option is the correct choice.

Normal lung function would present resonance, while conditions like pneumothorax (which involves air in the pleural space) and subcutaneous emphysema (which involves air under the skin) would result in hyper-resonance or tympanic sounds, rather than dullness. Understanding these distinctions helps in assessing lung health effectively.