What is auto-PEEP and in which patient population is it most common?

• A. Intrinsic PEEP from incomplete exhalation; common in COPD and severe asthma.
• B. Extrinsic PEEP from external valves; common in neonates.
• C. PEEP from high tidal volumes; common in healthy adults.
• D. Negative pressure at end expiration; common in athletes.

Answer: (A)

Auto-PEEP is intrinsic PEEP—the positive pressure present in the lungs at the end of expiration that arises without an external PEEP valve. It occurs when exhalation is incomplete and air becomes trapped, so end-expiratory pressure stays above baseline. This is especially common in obstructive lung diseases where airway resistance is high and expiration is slow, leading to dynamic hyperinflation. The classic populations are COPD and severe asthma, where the expiration time is frequently insufficient for complete emptying. It’s not due to external PEEP, nor to high tidal volumes alone, and it doesn’t involve negative pressure at end expiration.