A prospective, randomised trial of pre-oxygenation strategies available in the pre-hospital environment.

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.