Fig. 1.

Examples of flow (pink), airway pressure (P_aw blue), esophageal pressure (P_es, green), transpulmonary pressure (P_L, black) in patients with different breathing conditions (passive, active, or partially active). (A) Flow, P_aw, P_es, and P_L waveforms in a passive patient during volume assist control ventilation. Machine inflation creates a positive deflection on the P_es tracing that comes back to baseline during exhalation. (B) Flow, P_aw, P_es, and P_L waveforms in a patient breathing actively and triggering all of the breaths during pressure support ventilation. The patient’s effort creates a negative swing in the P_es tracing, triggering machine inflation. (C) Flow, P_aw, P_es, and P_L waveforms in a patient triggering the machine but not sustaining effort. The patient’s effort creates an initial negative swing in the P_es tracing. When the patient’s effort stops during the second phase of inspiration, the patient is passive and the machine inflation creates a positive pressure transmitted to the P_es, leading to a positive deflection. During exhalation, P_es goes back to baseline.