In pressure ventilation, a decrease in compliance leads to which outcome when ventilator settings are unchanged?

In pressure ventilation, a decrease in compliance leads to which outcome when ventilator settings are unchanged?

• A. Delivered tidal volume increases
• B. Peak inspiratory pressure decreases
• C. Delivered tidal volume decreases
• D. Inspiratory time shortens

Answer: (C)

In pressure ventilation, the volume you get with each breath depends on the applied inspiratory pressure and the lung–chest wall compliance. If compliance decreases (the system becomes stiffer) and you keep the same driving pressure, the lungs expand less for that pressure. The relationship is defined by ΔV = C × ΔP, where C is compliance and ΔP is the driving pressure. With a fixed ΔP and a lower C, ΔV (the tidal volume) decreases. So the delivered tidal volume goes down when compliance falls, while peak inspiratory pressure would not decrease under these unchanged settings (it may even rise if the same volume were needed), and inspiratory time isn’t the primary change here.

In pressure ventilation, the volume you get with each breath depends on the applied inspiratory pressure and the lung–chest wall compliance. If compliance decreases (the system becomes stiffer) and you keep the same driving pressure, the lungs expand less for that pressure. The relationship is defined by ΔV = C × ΔP, where C is compliance and ΔP is the driving pressure. With a fixed ΔP and a lower C, ΔV (the tidal volume) decreases.

So the delivered tidal volume goes down when compliance falls, while peak inspiratory pressure would not decrease under these unchanged settings (it may even rise if the same volume were needed), and inspiratory time isn’t the primary change here.