Which factor contributes to auto-PEEP?

Which factor contributes to auto-PEEP?

• A. Inadequate sedation.
• B. Too low FiO2.
• C. Incomplete expiratory emptying due to short expiratory time and high rate.
• D. Too high PEEP.

Answer: (C)

Auto-PEEP happens when air gets trapped in the lungs because expiration isn’t complete before the next breath begins. The most direct cause is incomplete expiratory emptying due to a short expiratory phase and a high respiratory rate. When you ventilate quickly, expiration time shortens, so the previous breath isn’t fully cleared. The leftover air raises the end-expiratory pressure inside the lungs, producing intrinsic PEEP. The other options don’t directly create this air trapping: too low FiO2 affects oxygen delivery, not the mechanics of expiration; inadequate sedation can increase patient effort or asynchrony but isn’t the primary mechanism of air trapping; and while high external PEEP can influence overall pressure and hyperinflation, it isn’t the fundamental cause of auto-PEEP—the issue is the insufficient time for expiration. To reduce auto-PEEP, lengthen expiratory time by lowering the respiratory rate or adjusting the I:E ratio to allow a longer expiration.

Auto-PEEP happens when air gets trapped in the lungs because expiration isn’t complete before the next breath begins. The most direct cause is incomplete expiratory emptying due to a short expiratory phase and a high respiratory rate. When you ventilate quickly, expiration time shortens, so the previous breath isn’t fully cleared. The leftover air raises the end-expiratory pressure inside the lungs, producing intrinsic PEEP.

The other options don’t directly create this air trapping: too low FiO2 affects oxygen delivery, not the mechanics of expiration; inadequate sedation can increase patient effort or asynchrony but isn’t the primary mechanism of air trapping; and while high external PEEP can influence overall pressure and hyperinflation, it isn’t the fundamental cause of auto-PEEP—the issue is the insufficient time for expiration. To reduce auto-PEEP, lengthen expiratory time by lowering the respiratory rate or adjusting the I:E ratio to allow a longer expiration.