Pleural effusion results in which of the following?

• A. Increased lung volume
• B. No effect on lung function
• C. Hyperventilation
• D. Decreased lung volume, atelectasis, and ineffective gas exchange

Answer: (D)

Fluid in the pleural space compresses the lung, limiting its expansion and reducing lung volume on the affected side. This compression can cause atelectasis (collapse of alveoli) and, with less aerated lung tissue, gas exchange becomes inefficient due to impaired ventilation-perfusion matching. Increased lung volume would not occur with a pleural effusion, and saying there’s no effect on lung function isn’t accurate because these mechanical changes clearly impair ventilation and oxygen exchange. Hyperventilation may occur if hypoxemia develops, but the defining description of a pleural effusion is decreased lung volume with atelectasis and impaired gas exchange.