A fixed-air CPAP releases air at a constant rate of pressure, regardless of whether or not you are breathing normally or experiencing a lapse in breathing. An APAP machine uses sensors and technology to determine when a person has slowed or stopped breathing. Then, the APAP adjusts its airflow accordingly. Since an APAP machine can detect when a person has stopped or slowed their breathing, it can also provide an estimate of how many abnormal breathing events a person experiences per night and per hour. The machine can also detect when the mask is leaking air.