The graphic above explains the difference between CPAP and Bi-Level PAP. CPAP requires the appropriate pressure to be set based on a pressure setting, titration sleep study. Once set, the CPAP pressure can ramp up from a low setting, typically over the first 5 to 30 minutes and then will stay constant at the prescribed setting. Bi-Level PAP is used to treat sleep apnea at above average pressure. High pressure is used on inhalation, then decreases dramatically on exhalation. Different versions of Bi-Level PAP can be used for treating Central Sleep Apnea and other versions have been prescribed as therapies for Respiratory Failure, Respiratory Insufficiency and CO2 retention.