Cycling of the mechanical ventilator breath.

Patient-ventilator interaction is a key element in optimizing mechanical ventilation. The change from inspiration to expiration is a crucial point in the mechanically ventilated breath, and is termed "cycling." Patient-ventilator asynchrony may occur if the flow at which the ventilator cycles to exhalation does not coincide with the termination of neural inspiration. Ideally, the ventilator terminates inspiratory flow in synchrony with the patient's neural timing, but frequently the ventilator terminates inspiration either early or late. Most current mechanical ventilators include adjustable cycling features that, when used in conjunction with waveform graphics, can enhance patient-ventilator synchrony.