Preoxygenation: a comparison of three different breathing systems

An end-tidal expiratory oxygen concentration (FE'(O 2)) greater than 0.90 i s considered to be adequate for preoxygenation. This is generally achieved using a face mask, but this can be unsatisfactory in some patients. We comp ared preoxygenation in 30 healthy volunteers using a face mask, the NasOral system, which is a novel preoxygenation device, and a mouthpiece with a no se-clip. We measured the maximal FE'(O 2), the FE'(O 2) after 2 min and the time to reach maximal FE'(O 2) and recorded the subjective judgement of th e volunteers. The maximal FE'(O 2) with face mask and mouthpiece was signif icantly greater than with the modified NasOral system (P<0.05 and P<0.01). With the former devices, a FE'(O 2) of 0.90 was achieved in 73% of the volu nteers vs 46% with the modified NasOral system. Using the mouthpiece, the F E'(O 2) after 2 min was significantly higher than using the face mask (P<0. 01) or the modified NasOral system (P<0.01). The time to maximal FE'(O 2) w as significantly shorter using the modified NasOral system than with the fa ce mask or mouthpiece (P<0.001 and P=0.0001). The volunteers gave more posi tive ratings to the face mask and mouthpiece than to the modified NasOral s ystem (P<0.001 and P<0.01). We conclude that the use of a mouthpiece can im prove preoxygenation in some patients. The results obtained with the modifi ed NasOral system do not justify its introduction into clinical practice.