Continuous positive pressure during anesthetic induction is today not routinely used partly a to the risk of gastric insufflation because of higher ventilatory pressures. However there are conflicting data with improvement of GERD symptoms in CPAP treated OSA patients. The investigators aim to compare the risk of gastric insufflation regarding mask ventilation technique, with or without positive end expiratory pressure. For measurements a High Resolution Impedance Manometry Catheter is used.