Increasing PEEP can improve oxygenation but may reduce cardiac output due to decreased venous return. Which statement best describes this trade-off?

• A. It increases cardiac output.
• B. It reduces venous return and can lower blood pressure.
• C. It has no effect on oxygenation.
• D. It improves oxygen delivery without any hemodynamic effects.

Answer: (B)

Increasing PEEP raises intrathoracic pressure, which helps recruit collapsed alveoli and improve oxygenation by enhancing functional residual capacity and V/Q matching. However, the same rise in intrathoracic pressure reduces venous return to the right heart, lowering preload, which can decrease cardiac output and may lead to lower blood pressure. This trade-off is exactly described by the statement that higher PEEP reduces venous return and can lower blood pressure. It’s not consistent with increases in cardiac output, it claims no effect on oxygenation, and it ignores potential hemodynamic changes while recognizing oxygenation gains, so it best captures the balance clinicians consider with PEEP.