In volume-controlled continuous mandatory ventilation (VC-CMV), breaths are delivered with a set tidal volume. Which parameter is fixed?

• A. Set tidal volume
• B. Set pressure
• C. Set rate
• D. Set inspiratory time

Answer: (A)

In volume-controlled continuous mandatory ventilation, the breath is delivered with a predetermined tidal volume on each cycle. That fixed volume is the parameter kept constant. The ventilator works to deliver that exact amount of air, so the pressure required to achieve it can vary from breath to breath depending on lung compliance and airway resistance. In contrast, the rate and the inspiratory time are settings that influence how the volume is delivered but are not the fixed target of this mode. So the key idea is that the tidal volume is the fixed, target value in VC-CMV.