Why might permissive hypercapnia be accepted during ARDS ventilation?

• A. Allows lower tidal volumes to minimize volutrauma; pH may be low but tolerated.
• B. Improves oxygen delivery
• C. Reduces the need for PEEP
• D. Lowers respiratory drive

Answer: (A)

Permissive hypercapnia is used to enable lung-protective ventilation in ARDS. By tolerating higher CO2 and a lower pH, clinicians can use smaller tidal volumes and avoid high airway pressures that cause volutrauma and barotrauma. The goal is to protect fragile, inflamed lungs while accepting a controllable degree of hypercapnia and acidosis. The body can often tolerate this mild acidosis because metabolic compensation helps over time, and buffering can be used if needed. Oxygenation is managed with FiO2 and PEEP, not by chasing higher CO2, so the gain comes from reducing ventilator-induced lung injury rather than directly improving oxygen delivery or changing respiratory drive.