When Delayed Cycling Makes a Failed Trigger Looks Like Early Cycling

These ventilator waveforms are from a patient on volume control mode. During the initial phase of inspiration, the airway pressure remains close to the baseline, indicating strong patient inspiratory effort. This is followed by a steep rise in pressure, likely due to relaxation of the inspiratory muscles and/or expiratory muscle contraction.

The flow–time scalar shows a small bump early in inspiration, suggesting that the ventilator briefly switched to a pressure support–like breath in response to the patient’s strong inspiratory effort, despite being in volume control mode.

In the expiratory flow–time scalar, an upward deflection appears as the patient attempts to initiate another breath unsuccessfully — a finding consistent with failed trigger.

A similar expiratory flow abnormality can be seen with early cycling dyssynchrony, where the initial inspiratory effort extends beyond the ventilator’s inspiratory phase, distorting the expiratory flow curve. However, in this case, the deflection results from a new inspiratory effort following the previous breath, rather than a continuation of the initial one — thereby mimicking early cycling but actually representing an ineffective trigger.