What variable signals the end of an inspiration by closing the inspiratory valve?

• A. Trigger Variable
• B. Baseline Variable
• C. Breath Triggers
• D. Cycle

Answer: (D)

The end of inspiration is governed by the cycle. The cycle is the criterion the ventilator uses to stop delivering inspiratory flow and switch to expiration, which happens when the inspiratory valve closes. Depending on mode, the cycle can be reached by reaching a set tidal volume (volume-cycled), when inspiratory flow falls to a small threshold (flow-cycled), or after a preset inspiratory time (time-cycled). Trigger variables and breath triggers are about starting a breath, not ending it, and a baseline variable isn’t a standard term used to signal the end of inspiration. So signaling the end by closing the inspiratory valve is the cycle.