What term describes the signal or target that ends inspiration and begins expiration?

• A. Exhalation
• B. Flow Controller Ventilation
• C. Cycle Variable
• D. Volume Cycling

Answer: (C)

Cycle variable is the signal that ends the current breath and starts expiration. It’s the control criterion the ventilator uses to terminate inspiration, and it can be based on different triggers depending on the mode—flow-based cycling ends inspiration when inspiratory flow falls to a threshold, while volume cycling ends inspiration when the preset tidal volume is delivered. Exhalation is simply the expiration phase that follows, not the trigger itself, and volume cycling is a specific way to end inspiration (based on reaching a set volume). The general term describing the terminating signal is cycle variable, which encompasses these different methods.