Preoxygenation: a comparison of three different breathing systems

An end-tidal expiratory oxygen concentration (FE'_O2) greaterthan 0.90 is considered to be adequate for preoxygenation. Thisis generally achieved using a face mask, but this can be unsatisfactoryin some patients. We compared preoxygenation in 30 healthy volunteersusing a face mask, the NasOral system, which is a novel preoxygenationdevice, and a mouthpiece with a nose-clip. We measured the maximalFE'_O2, the FE'_O2 after 2 min and the time to reach maximalFE'_O2 and recorded the subjective judgement of the volunteers.The maximal FE'_O2 with face mask and mouthpiece was significantlygreater than with the modified NasOral system (P<0.05 andP<0.01). With the former devices, a FE'_O2 of 0.90 was achievedin 73% of the volunteers vs 46% with the modified NasOral system.Using the mouthpiece, the FE'_O2 after 2 min was significantlyhigher than using the face mask (P<0.01) or the modifiedNasOral system (P<0.01). The time to maximal FE'_O2 was significantlyshorter using the modified NasOral system than with the facemask or mouthpiece (P<0.001 and P=0.0001). The volunteersgave more positive ratings to the face mask and mouthpiece thanto the modified NasOral system (P<0.001 and P<0.01). Weconclude that the use of a mouthpiece can improve preoxygenationin some patients. The results obtained with the modified NasOralsystem do not justify its introduction into clinical practice. Br J Anaesth 2001; 87: 928–31