During ventilation with a peak airway pressure of 50 cm H2O and PEEP of 5 cm H2O in a patient with VT of 600 mL and rate 14/min, which change most effectively reduces peak airway pressure without compromising alveolar ventilation?

During ventilation with a peak airway pressure of 50 cm H2O and PEEP of 5 cm H2O in a patient with VT of 600 mL and rate 14/min, which change most effectively reduces peak airway pressure without compromising alveolar ventilation?

• A. Increase the inspiratory flow rate
• B. Take off PEEP
• C. Reduce the I:E ratio (e.g., 1:3 to 1:2)
• D. Decrease VT to 300 mL and increase rate to 28/min

Answer: (C)

The key idea is that peak airway pressure in volume-controlled ventilation can be lowered by reducing the inspiratory flow while keeping the delivered tidal volume and minute ventilation the same. By lengthening the inspiratory time (increasing the I:E ratio from 1:3 toward 1:2), you push the same 600 mL of gas into the lungs over a longer period. The flow is slower, so the resistive pressure drop through the airways is smaller, and the peak pressure drops, while alveolar ventilation remains intact because tidal volume and rate are unchanged (dead space stays the same). Therefore, changing the I:E ratio to a less extreme inspiratory skew (1:2) lowers peak airway pressure without compromising ventilation. Increasing inspiratory flow would raise peak pressure, removing PEEP risks derecruitment and worsens ventilation, and reducing tidal volume with a higher rate can disrupt alveolar ventilation and does not reliably reduce peak pressure.

The key idea is that peak airway pressure in volume-controlled ventilation can be lowered by reducing the inspiratory flow while keeping the delivered tidal volume and minute ventilation the same. By lengthening the inspiratory time (increasing the I:E ratio from 1:3 toward 1:2), you push the same 600 mL of gas into the lungs over a longer period. The flow is slower, so the resistive pressure drop through the airways is smaller, and the peak pressure drops, while alveolar ventilation remains intact because tidal volume and rate are unchanged (dead space stays the same).

Therefore, changing the I:E ratio to a less extreme inspiratory skew (1:2) lowers peak airway pressure without compromising ventilation. Increasing inspiratory flow would raise peak pressure, removing PEEP risks derecruitment and worsens ventilation, and reducing tidal volume with a higher rate can disrupt alveolar ventilation and does not reliably reduce peak pressure.