When the ventilator terminates the inspiratory phase prematurely, the patient may continue the inspiratory effort, producing an upward deflection in the expiratory flow–time scalar — a form of dyssynchrony known as early cycling

The expiratory flow–time scalar shows a small upward deflection early in expiration, which could be mistaken for early cycling dyssynchrony. However, a closer look at the inspiratory flow–time scalar reveals two distinct flow peaks. The first peak corresponds to the initial inspiratory effort, while the second peak represents a new inspiratory effort that begins just before the ventilator cycles to expiration and continues into the expiratory phase, creating waveform changes

Normal expiration is a passive process, characterized by an exponential decay of expiratory flow. However, in the presence of active exhalation, the expiratory flow increases, and this is often accompanied by a rise in baseline airway pressure due to the elevated intrathoracic pressure generated by expiratory muscle contraction.

In pressure support mode, cycling to expiration occurs when the inspiratory flow decreases to a preset percentage of the peak inspiratory flow. However, in the presence of an air leak, the flow may fail to drop to the preset threshold, as the ventilator continues to deliver additional flow to maintain the target pressure and compensate for the leak. This results in a prolonged inspiratory phase and delayed cycling. In this example, the pressure–time scalar shows a notch durin

These waveforms illustrate multiple patient–ventilator dyssynchronies, highlighting the consequences of inappropriate ventilator settings. In the pressure–time scalar, immediately after the breath is triggered, the airway pressure drops to the level of PEEP, indicating a strong inspiratory effort and significant work shifting from the ventilator to the patient. This is followed by a steep rise in pressure, which reflects inspiratory muscle relaxation and expiratory muscle con

Breaths 2 and 5 in the following waveforms demonstrate a marked pressure drop below baseline, accompanied by higher peak inspiratory flow and a rapid return of flow to baseline compared to the surrounding breaths. When such brief, strong inspiratory efforts are observed, it is important to consider hiccups as the cause, since hiccups generate sudden, short-duration diaphragmatic contractions that produce this characteristic waveform pattern