Pressure versus flow triggering and work of breathing

Flow, Pao, Pes, and Pdi traced over time during flow triggered (on right) and pressure triggered (on left) spontaneous ventilation. The portion of the deflection in Pes and Pdi from on first solid vertical line on the left, to the dashed line, represents the deflection between the initiation of inspiratory effort to the beginning of flow (dynamic PEEPi). Note that this deflection is smaller for Pes and Pdi during flow triggered (right) than pressure triggered (left) spontaneous breathing, hence imposing less work of breathing for the patient.