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PAP therapy is a prescribed treatment because the air pressure required to stabilize the airway, known as the therapeutic pressure, is different for everyone. The treatment pressure is measured in centimeters of water (cm H2O) and most machines can be set by the provider to deliver pressures between 4 and 20cm H2O. The correct setting is critical because if the air pressure is set too low, the airway can still collapse. If it's set too high, you can become over-ventilated. Either scenario will have a negative impact on your sleep quality. Several factors impact the therapeutic pressure, including severity of OSA and structure of the airway. An individual's therapeutic level is determined during a continuous positive airway pressure (CPAP) titration sleep study.