The APAP still pumps air through a mask worn over the face. However, this machine will adjust the pressure you receive by averaging the pressures needed during your preceding breaths. In theory this automated device sounds as if it better mirrors the changing requirements of one’s lifestyle. If you gain weight the machine will adjust for it and provide increased pressure. Too much alcohol and again it will provide more pressure. Generally speaking the pressures that it provides are the same for both inspiration and expiration. It does not function as a BIPAP. Most patient that use CPAP/BIPAP do not find that their pressures change very much. Even with excessive drinking or moderate weight gain. Some patients find a lag in pressure from machines that are automated. Especially in patients requiring high pressures, the CPAP is frequently more comfortable.