There are two main CPAP machine types used to treat obstructive sleep apnea. CPAP stands for Continuous Positive Airway Pressure. Depending on the user, the pressure required to maintain the airway in an open position can be Fixed, or change Automatically to the required pressure throughout the night. Therefore, we classify machines as either Fixed Pressure (CPAP) or Automatic (APAP), however both are commonly referred to as CPAP Machines.