title: A prospective, randomised trial of pre-oxygenation strategies available in the pre-hospital environment.
abstract: Pre-oxygenation before tracheal intubation aims to increase safe apnoea duration by denitrogenation of the functional residual capacity of the lungs, and increasing oxygen stores at the onset of apnoea. Pre-oxygenation options in the pre-hospital environment are limited due to oxygen availability and equipment portability. The aim of this study was to evaluate the effectiveness of strategies available in this setting. This was a prospective, randomised, crossover study of 30 healthy volunteers who underwent 3-min periods of pre-oxygenation by tidal volume breathing with a non-rebreather mask, a bag-valve-mask and a portable ventilator. The primary outcome measure was fractional expired oxygen concentration of the first exhaled breath after each technique. The secondary outcome measure was ease of breathing, assessed using a visual analogue scale. The mean (95%CI) fractional expired oxygen concentrations achieved with the non-rebreather mask were 64 (60-68)%, bag-valve-mask 89 (86-92)% and portable ventilator 95 (94-96)%. Pre-oxygenation efficacy with the non-rebreather mask was significantly worse than with either the bag-valve-mask (p < 0.001) or ventilator (p < 0.001). No significant difference in ease of breathing was identified between the bag-valve-mask and ventilator, but both were perceived as being significantly more difficult to breathe through than the non-rebreather mask. We conclude that, in healthy volunteers, the effectiveness of pre-oxygenation by bag-valve-mask and portable ventilator was superior to pre-oxygenation with a non-rebreather mask, although the non-rebreather mask was easier to breathe through than the other pre-oxygenation devices.
authors.affiliation: London's Air Ambulance, Bart's Health NHS Trust, London, UK.|Essex and Herts Air Ambulance Trust, UK.
authors.forename: C J
authors.initials: CJ
authors.lastname: Groombridge
authors.affiliation: Essex and Herts Air Ambulance Trust, UK.
authors.forename: E
authors.initials: E
authors.lastname: Ley
authors.affiliation: Kent Surrey and Sussex Air Ambulance Trust, Marden, UK.
authors.forename: M
authors.initials: M
authors.lastname: Miller
authors.affiliation: London's Air Ambulance, Bart's Health NHS Trust, London, UK.
authors.forename: T
authors.initials: T
authors.lastname: Konig
mesh_terms: D000328:Adult; D058109:Airway Management / Q000295:instrumentation / Q000379:methods*; D018592:Cross-Over Studies; D004632:Emergency Medical Services; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D007442:Intubation, Intratracheal; D017214:Laryngeal Masks; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption; D011446:Prospective Studies; D012119:Respiration; D012121:Respiration, Artificial / Q000295:instrumentation / Q000379:methods*; D013990:Tidal Volume; D055815:Young Adult
keywords: airway management; emergency medical services; oxygen inhalational therapy; tracheal intubation