Which ventilator mode is least suitable for a patient experiencing auto-PEEP due to air trapping?

• A. PEEP
• B. APRV
• C. Volume assist control
• D. CMV

Answer: (C)

Auto-PEEP from air trapping happens when the lungs don’t have enough time to fully exhale before the next breath begins, so air accumulates and intrathoracic pressure rises. The aim is to give breaths that allow a longer expiratory phase and minimize breath stacking.

Volume assist-control delivers a fixed tidal volume with a set inspiratory time on every breath. In a patient with auto-PEEP, if the patient tries to breathe spontaneously or if the next breath arrives before exhalation is complete, breaths can stack on top of each other. This increases the end-expiratory lung volume and intrinsic PEEP, worsening hyperinflation and the work of breathing. Because of that fixed, timer-driven pattern, this mode is least suitable for someone with airway trapping.

Other modes that emphasize shorter inspiratory times, longer expiratory times, and allowance for spontaneous breathing help reduce air trapping and support exhalation. Extrinsic PEEP can be used carefully to balance pressures without pushing more air in, and controlled modes can be adjusted to avoid breath stacking.