Which cycling terminates breath when the pressure limit is reached and acts as a safety mechanism?

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

Answer: (D)

Breath cycling in ventilators is about when the inspiratory phase ends. The mechanism that stops inspiration as soon as a preset airway pressure is reached is pressure cycling. This acts as a safety mechanism to prevent airway pressures from climbing too high and risking lung injury. As the breath begins, pressure rises; once the chosen limit is reached, the ventilator ends the breath and switches to exhalation, even if the desired volume or flow hasn’t been exactly met. Other cycling methods exist: ending by a volume target is about reaching a set tidal volume, ending by a low flow threshold is flow cycling, and ending by a fixed time is time cycling. Exhalation is simply the subsequent phase, not the method that terminates inspiration.