Comparison of preoxygenation using a tight facemask, humidified high-flow nasal oxygen and a standard nasal cannula – a volunteer, randomised, crossover study

BACKGROUND Preoxygenation before anaesthesia induction is routinely performed via a tight-fitting facemask or humidified high-flow nasal oxygen. We hypothesised that effective preoxygenation, assessed by end-tidal oxygen (EtO 2 ) levels, can also be performed via a standard nasal cannula. OBJECTIVE This study compared the efficacy of preoxygenation between a traditional facemask, humidified high-flow nasal oxygen and a standard nasal cannula. DESIGN A volunteer, randomised, crossover study. SETTING Karolinska University Hospital, Stockholm. The study was conducted between 2 May and 31 May 2023. PARTICIPANTS Twenty cardiopulmonary healthy volunteers aged 25–65 years with a BMI <30. INTERVENTIONS Preoxygenation using a traditional facemask, humidified high-flow nasal oxygen and standard nasal cannula. Volunteers were preoxygenated with all three methods, at various flow rates (10–50 l min −1 ), with open and closed mouths and during vital capacity manoeuvres. MAIN OUTCOME MEASURES The study's primary outcome compared the efficacy after 3 min of preoxygenation, assessed by EtO 2 levels, between the three methods and various flow rates of preoxygenation. RESULTS Three methods generated higher EtO 2 levels than others: (i) facemask preoxygenation using normal breathing, (ii) humidified high-flow nasal oxygen, closed-mouth breathing, at 50 l min −1 and (iii) standard nasal cannula, closed-mouth breathing, at 50 l min −1 , and expressed as means (SD): 90% (3), 90% (6) and 88% (5), respectively. Preoxygenation efficacy was greater via the bi-nasal cannulae using closed vs. open mouth breathing as well as with 3 min of normal breathing vs. eight vital capacity breaths. Preoxygenation with a facemask and humidified high-flow nasal oxygen was more comfortable than a standard nasal cannula. CONCLUSION The efficacy of preoxygenation using a standard nasal cannula at high flow rates is no different to clinically used methods today. The standard nasal cannula provides less comfort but is highly effective and could be an option when alternative methods are unavailable. TRIAL REGISTRATION Clinicaltrials.gov, NCT05839665.