Comparison of pre-oxygenation using spontaneous breathing through face mask and high-flow nasal oxygen: A prospective randomised crossover controlled study in healthy volunteers

BACKGROUND High-flow nasal oxygen (HFNO) therapy has been proposed for pre-oxygenation before intubation, but the end-tidal fraction of oxygen (ETO2) obtained remains unknown. OBJECTIVE(S) To compare the ETO2 following a 3 min pre-oxygenation with HFNO and face mask. SETTING Operating room in a primary university hospital. DESIGN A prospective, randomised crossover study. PARTICIPANTS Fifty healthy volunteers. INTERVENTIONS Participants were randomly pre-oxygenated through spontaneous breathing 100% oxygen in a face mask and with HFNO (mouth closed, heated and humidified gas flow at 60 l min–1). In the face mask group, the ETO2 was measured continuously. In the HFNO group, the nasal cannula was quickly exchanged with a face mask while the subject held their breath at end inspiration and the ETO2 was measured after a deep expiration. The protocol ended when ETO2 reached 90% or otherwise at 6 min. MAIN OUTCOME MEASURES The primary endpoint was the ETO2 after 3 min of pre-oxygenation. Secondary endpoints were the proportion of participants with an ETO2 at least 90% and the time until the ETO2 at least 90%. RESULTS The ETO2 after 3 min of pre-oxygenation was 89 (2) % and 77 (12) % in the face mask and HFNO groups [difference 12% (95% confidence interval, 95% CI: 8 to 15]; P 

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