title: Efficacy of Nasal Cannula Oxygen as a Preoxygenation Adjunct in Emergency Airway Management.
abstract: Although preoxygenation for emergency airway management is usually performed with nonrebreather face masks or bag-valve-mask devices, some clinicians also deliver supplemental high-flow oxygen by nasal cannula. We aim to measure the efficacy of supplemental nasal cannula oxygen delivery to conventional bag-valve-mask and nonrebreather face mask preoxygenation both with and without a simulated face mask leak.
  
  
  
  We conducted a randomized crossover trial using healthy volunteers. We randomized subjects to preoxygenation with bag-valve-mask or nonrebreather face mask. In random sequence, subjects underwent 3-minute trials of preoxygenation with oxygen through mask alone at 15 L/min, oxygen through mask at 15 L/min with standardized leak, oxygen through mask at 15 L/min+oxygen through nasal cannula at 10 L/min, and oxygen through mask at 15 L/min+oxygen through nasal cannula at 10 L/min with standardized leak. The primary outcome was single-breath exhalation end-tidal oxygen (eto2). We compared eto2 between preoxygenation modalities, using nonparametric techniques.
  
  
  
  We enrolled 60 subjects (30 nonrebreather face mask and 30 bag-valve-mask). In scenarios without a mask leak, eto2 was similar between bag-valve-mask and bag-valve-mask+nasal cannula (mean 79% versus 75%; difference -3%; 95% confidence interval [CI] -8% to 1%). In bag-valve-mask scenarios with a mask leak, eto2 was higher for bag-valve-mask+nasal cannula than bag-valve-mask alone (mean 66% versus 41%; difference 25%; 95% CI 21% to 29%). eto2 was higher for nonrebreather face mask+nasal cannula than nonrebreather face mask (mean 67% versus 52%; difference 15%; 95% CI 12% to 18%). In nonrebreather face mask scenarios with a mask leak, eto2 was higher for nonrebreather face mask+nasal cannula than nonrebreather face mask (mean 65% versus 48%; difference 17%; 95% CI 13% to 20%).
  
  
  
  Although not aiding bag-valve-mask preoxygenation with a good mask seal, supplemental nasal cannula oxygen improved preoxygenation efficacy in the presence of a bag-valve-mask mask leak. Supplemental nasal cannula oxygen improved nonrebreather face mask preoxygenation both with and without a mask leak. Supplemental nasal cannula oxygen may be helpful for preoxygenation before emergency airway management.
authors.affiliation: Retrieval Medicine, Greater Sydney Area Helicopter Emergency Medical Service, New South Wales Ambulance, Australia. Electronic address: clarehayesbradley@yahoo.com.
authors.forename: Clare
authors.initials: C
authors.lastname: Hayes-Bradley
authors.affiliation: Department of Anaesthesia, St George Hospital, Sydney, New South Wales, Australia.
authors.forename: Anthony
authors.initials: A
authors.lastname: Lewis
authors.affiliation: Retrieval Medicine, Greater Sydney Area Helicopter Emergency Medical Service, New South Wales Ambulance, Australia; Sydney Medical School, Sydney University, Australia.
authors.forename: Brian
authors.initials: B
authors.lastname: Burns
authors.affiliation: Retrieval Medicine, Greater Sydney Area Helicopter Emergency Medical Service, New South Wales Ambulance, Australia; Department of Anaesthesia, St George Hospital, Sydney, New South Wales, Australia.
authors.forename: Matt
authors.initials: M
authors.lastname: Miller
mesh_terms: D000328:Adult; D000072601:Cannula; D018592:Cross-Over Studies; D004638:Emergency Treatment / Q000295:instrumentation*; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D008397:Masks; D010100:Oxygen / Q000008:administration & dosage*; D012121:Respiration, Artificial / Q000295:instrumentation* / Q000379:methods; D016896:Treatment Outcome
chemical_list: D010100:Oxygen