When you've been prescribed a CPAP machine to use for sleep apnea treatment, it's important that you have your machine calibrated before you use it. The calibration process is designed to regulate the pressure of the air to meet your specific breathing needs. Some people need constant positive pressure, while others need to have intermittent pressure so that the pressure lessens on the exhale. Here's a look at what you need to know about your CPAP machine's calibration and pressure settings.