This is a machine that consists of a simple pump that flows air into a mask that is worn over the nose and/or mouth. It is designed to pressurize your airway so that when you exhale the passage remains open as a result of this pressure. You can get a sense of this if you ever inflated air mattress. When you exhale into the valve it becomes harder to push out the air as the pressure in the mattress increases. The same is true when the setting on the CPAP machine is increased. When set properly, it can results in complete resolution of the Obstructive Sleep Apnea.