High-flow nasal cannula versus face mask for preoxygenation in obese patients: A randomised controlled trial.

BACKGROUND: Preoxygenation efficacy with high-flow nasal cannula (HFNC) in obese patients is not clearly established. The primary aim of this study was to compare heated, humidified, high-flow nasal cannula with face mask for preoxygenation in this population.

METHODS: We conducted a single-centre, randomised, controlled trial. Forty subjects with BMI ≥ 35 kg m-2 were randomly assigned to receive 5.0 min of preoxygenation with face mask and 7 cm H2 O of PEEP (PEEP group) or HFNC at 70 L min-1 (HF group). Following induction, bag-mask ventilation continued until laryngoscopy, whereas HFNC was maintained before and during intubation. The primary outcomes were end-tidal fraction of oxygen (EtO2 ) at 2.5 and 5.0 min duration of preoxygenation. Secondary outcomes included PaO2 and PaCO2 at 2.5 and 5.0 min of preoxygenation and at intubation.

RESULTS: Mean (±SD) EtO2 was 0.89 (±0.04) versus 0.90 (±0.05) after 2.5 min (95% CI for mean difference -0.02, 0.04) and 0.93 (±0.02) versus 0.91 (±0.02) after 5.0 min of preoxygenation (95% CI for mean difference -0.03, -0.002) in the PEEP (n = 18) and HF group (n = 20), respectively. All subjects reached an EtO2  ≥ 0.85 at 5.0 min. There were no differences in mean PaO2 or PaCO2 during preoxygenation. Subjects in the HF group had a mean (±SD) apnoea time of 199 (±38) s, but no desaturation (SpO2  < 100%) occurred.

CONCLUSIONS: Face mask with PEEP was superior to HFNC for preoxygenation in obese subjects. HFNC provided adequate preoxygenation quality in all subjects and may be considered as an alternative to face mask in selected patients.

TRIAL REGISTRATION: #ISRCTN37375068 (www.isrctn.com).