A comparison of bag mask and mouth mask ventilation in anaesthetised patients.

Anaesthetic residents used bag valve mask (BVM) or mouth mask (MM) ventilation, both with an O2 flow of 15 l min-1 to ventilate 30 ASA I or II anaesthetised patients for 4 min prior to endotracheal intubation. Mean nasopharyngeal O2 was higher with BVM (BVM 95% (S.D. 3%) MM 54% (S.D. 12%)). End tidal CO2 (ETCO2) was similar in both groups (ETCO2% at 4 min: BVM 4.65 (S.D. 0.84) MM 4.53 (S.D. 0.54)) but respiratory rate was faster with BVM (BVM 17 min-1 (S.D. 5) MM 12 min-1 (S.D. 4)). Peak (Paw) and mean (Paw) airway pressures were higher with MM and MM produced significant expiratory pressure [cmH2O: BVM Paw 16.7 (S.D. 5.3) Paw 4.2 (S.D. 2.1) MM: Paw 20.9 (S.D. 5.2) Paw 7.8 (S.D. 2.1)) minimum expiratory pressure: MM 2.4 (S.D. 1.1) BVM 0.2 (S.D. 0.4). Gastric insufflation was detected in two MM and two BVM patients. This tended to be more severe with MM ventilation. Although MM ventilation has some important disadvantages it can be used effectively by resuscitators with little or no experience in its use.