What is the primary purpose of increasing extrinsic PEEP?

• A. To prevent end-expiratory alveolar collapse and improve oxygenation
• B. To decrease mean airway pressure
• C. To reduce tidal volume
• D. To lower PIP

Answer: (A)

Applying extrinsic PEEP keeps airways open at the end of exhalation, which prevents alveolar collapse and recruits more alveoli for gas exchange. By keeping these units inflated, the functional residual capacity increases and the amount of blood that bypasses poorly ventilated areas (shunt) decreases, leading to better oxygenation.

This approach also raises the mean airway pressure, which supports sustained alveolar recruitment and improves oxygen delivery, but it can come with trade-offs like potential reductions in venous return and cardiac output if PEEP is too high. It’s not about lowering mean airway pressure or directly reducing tidal volume or peak inspiratory pressure—the primary aim is stabilizing alveoli at end expiration to enhance oxygenation.