The variable that terminates inspiration in a ventilator is called what?

• A. Cyclic pattern
• B. Cycling Mechanism
• C. Trigger Variable
• D. End-Inspiratory Switch

Answer: (B)

Ending inspiration is controlled by the cycling mechanism—the criterion the ventilator uses to switch from delivering breath to expiration. The trigger starts inspiration, and the cycling mechanism determines when that inspiration ends. In different modes this ending condition can be reaching the set tidal volume, a fall in inspiratory flow to a low threshold, or a predefined inspiratory time. Because this mechanism is what actually stops inspiration and hands control to expiration, it’s the correct term to describe the variable that terminates inspiration.