Preoxygenation by spontaneous breathing or noninvasive positive pressure ventilation with and without positive end-expiratory pressure: A randomised controlled trial

BACKGROUNDIn emergency situations requiring rapid airway control, shortening preoxygenate time is desirable. OBJECTIVESThe objective of this study is to compare the time to achieve an expired O2 fraction FeO2 of 90% (FeO2 90%) during preoxygenation with spontaneous breathing and positive pressure ventilation with and without positive end-expiratory pressure (PEEP). DESIGNA randomised controlled trial. SETTINGPrimary care in a university hospital in France from October 2006 to January 2008. PATIENTSAdults patients scheduled for elective surgery. Exclusion criteria were rapid sequence induction, anticipated difficult airway management and refusal to provide consent. INTERVENTIONPatients were randomly allocated to preoxygenation with spontaneous breathing or positive pressure ventilation (positive inspiratory pressure12 cmH2O) without PEEP and with PEEP (positive inspiratory pressure12 cmH2O, PEEP6 cmH2O). MAIN OUTCOME MEASURESTime to achieve an expired O2 fraction of 90% measured from positioning the face mask, and the time it took after endotracheal intubation for the SpO2 to fall to 93% (SpO2 93%) while the patient was apnoeic. Patient discomfort was recorded (visual analogue scale). Data are median (quartile 25th to 75). RESULTSThe time to achieve an FeO2 90% was shorter with positive pressure ventilation, with PEEP [140 (100 to 200) s] and without PEEP [153 (120 to 218) s], than with spontaneous breathing [190 (130 to 264) s; P = 0.002]. At 3 min, 47, 60 and 74% of patients achieved an FeO2 of 90% or more in the spontaneous breathing, positive pressure ventilation without and with PEEP groups, respectively (P = 0.01). Cox proportional-hazards regression showed that positive pressure ventilation with PEEP [hazard ratio 2.18; 95% confidence interval (95% CI) 1.42 to 3.36); P