Which cycling terminates breath when flow drops to a specific percentage of its peak?

• A. Time Cycling
• B. Exhalation
• C. Flow Cycling
• D. Volume Limit

Answer: (C)

Flow cycling ends the inspiratory phase based on the rate of air flow falling to a small fraction of its peak. In this mode, the ventilator delivers a breath until the inspiratory flow decays to a preset percentage of the maximum flow reached at the start of inspiration, commonly around 25–30%. When the flow drops to that threshold, the inhalation stops and expiration begins. This approach allows the breath to terminate in concert with how the patient’s airway mechanics and effort change, providing a more natural cycle that can adapt to varying compliance and resistance.

Time cycling ends after a set inhalation time, volume limit ends when a target tidal volume is delivered, and exhalation is not a cycling method. Thus, termination by a specific percentage of peak flow is characteristic of flow cycling.