A CPAP is a small air pump attached to a face mask that fits over the nose and mouth and forces air through the passages or blows the airways open during sleep. There are actually several types of CPAP machines. An AUTO-PAP is a CPAP that senses an apnea or snoring event and ramps up the pressure until the events cease. It will then slowly reduce pressure and/or increase pressure until it finds the optimum pressure for you for that night.