Bi-level positive airway pressure (BiPAP) in Bipap Machine :  Due to Bilevel Positive Airway Pressure, i.e. Bipap these sleep apnea machines known as Bipap machine. Bipap Machine works on 2 positive airway pressures(also known as Bilevel bi-level positive airway pressure): IPAP(Inhale Positive Airway Pressure) - This pressure is to Inhale in Bipap Machines. EPAP (Exhale Positive Airway pressure) - This Pressure is for Exhale  in Bipap Machines. That's why Bipap machine has 2 different settings for positive airway pressure, one is for IPAP(inhale airway pressure) and second is EPAP(exhale Airway pressure).