Which statement about permissive hypercapnia and ventilator-induced lung injury is true?

• A. Allowing CO2 to rise helps minimize ventilator-induced lung injury
• B. Maintaining strict normocapnia always improves outcomes
• C. Higher CO2 levels are associated with increased cerebral injury in all patients
• D. CO2 levels are irrelevant to lung protection strategies

Answer: (A)

Permissive hypercapnia is a lung-protective ventilation approach that accepts higher CO2 levels to prevent ventilator-induced lung injury. By using lower tidal volumes and limiting plateau pressures, the lungs are less overdistended, which reduces volutrauma, barotrauma, and the inflammatory biotrauma that contribute to VILI. The mild acidosis from CO2 retention is generally tolerated and can be managed, while the benefit of protecting the lung often outweighs the downside in appropriately selected patients. That’s why allowing CO2 to rise is considered helpful for minimizing lung injury.

If you push for strict normocapnia, you may need higher airway pressures or larger tidal volumes, which can increase the risk of lung injury. CO2 levels aren’t irrelevant to protection strategies; they’re a critical part of balancing lung protection with physiologic needs. The statement about cerebral injury is not universal, since the neurological impact of hypercapnia varies with the clinical context and the patient’s condition.