Sensitivity in mechanical ventilation is typically set by triggering either a pressure or a flow change. Which option describes this?

• A. -1 to -2 cmH2O
• B. 2-5 L/min
• C. Pressure or Flow
• D. Volume or Time

Answer: (C)

Sensitivity determines how easily the ventilator recognizes the patient’s effort to breathe, and it is set by triggering a change in either airway pressure or inspiratory flow. The concept that fits this description is that triggering can be done by either pressure or flow changes. Pressure triggering uses a small drop in airway pressure below the baseline (around -1 to -2 cmH2O) to start a breath, while flow triggering uses a slight change in inspiratory flow (typically about 2–5 L/min) to initiate inspiration. The other options give specific numeric thresholds or refer to parameters (volume or time) that don’t define how sensitivity works.