Airway pressure release ventilation (APRV)

A: Continuous flow positive airway pressure (CPAP). B: During exhalation with CPAP, the CPAP valve opens and the airway pressure release (APR) valve closes. C: During airway pressure release from the preset CPAP level to ambient pressure, the CPAP valve closes and the APR valve opens. After closure of the APR valve, functional residual capacity (FRC) is re-established.