In emergency situations requiring rapid airway control, shortening preoxygenate time is desirable.

The 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).

A randomised controlled trial.

Primary care in a university hospital in France from October 2006 to January 2008.

Adults patients scheduled for elective surgery. Exclusion criteria were rapid sequence induction, anticipated difficult airway management and refusal to provide consent.

Patients were randomly allocated to preoxygenation with spontaneous breathing or positive pressure ventilation (positive inspiratory pressure: 12 cmH2O) without PEEP and with PEEP (positive inspiratory pressure: 12 cmH2O, PEEP: 6 cmH2O).

Time 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).

The 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 in, 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 < 0.001] and without PEEP (hazard ratio 1.62; 95% CI 1.05 to 2.50; P = 0.03) were associated with a shorter time to an FeO2 90%. The time until SpO2 93% was not significantly different between spontaneous breathing [305 (263 to 383) s], positive pressure ventilation without PEEP [370 (300 to 450) s] and with PEEP [345 (245 to 435) s; P = 0.08]. The discomfort reported was 0 (0 to 18) mm and was comparable between groups (P = 0.22).

Compared with spontaneous breathing, positive pressure ventilation with and without PEEP shortened preoxygenation time.

Clinicaltrials.gov identifier: NCT02313766.