This identifies the machine as continuous, auto adjusting, or bilevel operation. This does not identify whether the machine automatically adjusts pressure. Auto adjusting refers to APAP, whereas BiPAP Auto is differentiated using the Auto Pressure Adjustment property. BiPAP machines are defined further using Spontaneous or Timed properties. A CPAP machine blows one constant pressure of air into your passageway throughout the night. Your ideal pressure was determined during your sleep study. A BiPAP machine delivers two separate pressures of air; One when the patient inhales and a separate pressure when they exhale. The machine alternates between the two set pressures to help optimize your sleep apnea treatment. An APAP machine automatically adjusts on a breath by breath basis to blow the minimum pressure needed to keep your airway open during sleep. This allows your machine to provide you with your ideal pressure nightly.