Flow Cycling Simplified

In pressure support mode, the ventilator terminates inspiration when the flow decreases to a predetermined percentage of the peak inspiratory flow (end inspiration/ expiratory trigger sensitivity). For instance, if the peak inspiratory flow is 60 litres per minute and the cycling setting is 25%, the ventilator concludes the inspiratory phase when the flow reaches 15 litres per minute.

Some ventilators come with a default cycling setting of 25%.

Adjusting the cycling setting to a higher percentage leads to earlier termination of inspiration, while a lower percentage prolongs inspiration. In COPD patients, a higher percentage of end inspiration setting is advisable to allow more time for exhalation. Conversely, a lower percentage of end inspiration setting is recommended for restrictive disorders.