A pleural effusion that is large can cause which of the following?

A pleural effusion that is large can cause which of the following?

• A. Hemodynamic compromise
• B. Hypoventilation
• C. Hyperinflation
• D. Hypoxemia only

Answer: (A)

When a pleural effusion is large, the accumulating fluid creates a mass effect inside the chest that can impede venous return to the heart. This decreases preload and cardiac output, potentially leading to hemodynamic instability or shock if the condition is severe. The fluid raises intrathoracic pressure and can compress the heart and great vessels, so impaired circulation becomes the key clinical consequence. Hypoventilation can occur because lung compression reduces inspiratory capacity, but it is not the dominant or most dramatic effect; hyperinflation is unlikely since the lung is compressed rather than expanded. Hypoxemia can result from V/Q mismatch due to lung atelectasis, but the question asks for the principal physiologic consequence, which is the compromise in hemodynamics due to impaired venous return.

When a pleural effusion is large, the accumulating fluid creates a mass effect inside the chest that can impede venous return to the heart. This decreases preload and cardiac output, potentially leading to hemodynamic instability or shock if the condition is severe. The fluid raises intrathoracic pressure and can compress the heart and great vessels, so impaired circulation becomes the key clinical consequence.

Hypoventilation can occur because lung compression reduces inspiratory capacity, but it is not the dominant or most dramatic effect; hyperinflation is unlikely since the lung is compressed rather than expanded. Hypoxemia can result from V/Q mismatch due to lung atelectasis, but the question asks for the principal physiologic consequence, which is the compromise in hemodynamics due to impaired venous return.