During conventional mechanical ventilation, which parameter is most effective for improving oxygenation?

• A. Inspiratory time
• B. Ventilator rate
• C. Mean airway pressure
• D. Tidal volume

Answer: (C)

Oxygenation on conventional ventilation is driven most by mean airway pressure because it reflects how long and how intensely the lungs are exposed to positive pressure each breath, which determines alveolar recruitment and the surface area available for gas exchange. Increasing mean airway pressure—primarily by raising PEEP and, when appropriate, adjusting inspiratory time or peak pressures—keeps alveoli open longer during the cycle, reduces shunt, and improves PaO2. In contrast, inspiratory time and ventilator rate mainly affect ventilation and CO2 removal, not oxygenation, and while tidal volume can influence MAP to some extent, pushing tidal volume upward risks lung injury and does not improve oxygenation as directly as increasing MAP does. So, the most effective lever for boosting oxygenation is increasing mean airway pressure.