Pre-oxygenation using face mask or mouthpiece with and without nose clip: patient preferences and efficacy.

We assessed the effectiveness of mouthpieces for oxygenation before induction of anaesthesia. In part 1 of the study we asked 52 day case patients whether they would prefer mask, mouthpiece, or mouthpiece with nose clip, and which they would be willing to use. In part 2 we pre-oxygenated 18 volunteers using each of the three methods in a crossover study. We measured time to 90% end tidal oxygen concentration (FE'O2), or maximum FE'O2 after 3 min if less than 90%. Of the patients surveyed, 20 (39%) preferred mask, 23 (44%) mouthpiece, one mouthpiece with nose clip and nine (17%) expressed no preference. Only 88% would be willing to use the face mask, but all would accept either the face mask or the mouthpiece with nose clip. In part 2 of the study, the mouthpiece alone proved significantly worse than the mask or mouthpiece with nose clip. The latter two did not differ significantly. Offering the alternative of mouthpiece with nose clip would increase patient acceptance of effective pre-oxygenation.