Airway pressure and flow as a function of time using the Drager Evita 4 Pulmonary Workstation in APRV mode. Note that the upper tracing indicates airway pressure, while the lower trace represents flow over time. The airway pressure is held relatively constant, while the patient is able to breathe spontaneously. The interruption in the airway pressure trace marks the airway pressure release phase, and is short relative to the time spent at the higher pressure. Reproduced with permission from Drager, Inc.