LAUSR

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.