A Practical Solution for Preoxygenation in the Prehospital Setting: A Nonrebreather Mask with Flush Rate Oxygen

Prehospital clinicians need a practical means of providing adequate preoxygenation prior to intubation. A bag-valve-mask (BVM) can be used for preoxygenation in perfect conditions but is likely to fail in emergency settings. For this reason, many airway experts have moved away from using BVM for preoxygenation and instead suggest using a nonrebreather (NRB) mask with flush rate oxygen.Literature on preoxygenation has suggested that a NRB mask delivering flush rate oxygen (on a 15 L/min O₂ regulator, maximum flow, ∼50 L/min) is noninferior to BVM at 15 L/min held with a tight seal. However, in the prehospital setting, where emergency airway management success varies, preoxygenation techniques have not been deeply explored. Our study seeks to determine whether preoxygenation can be optimally performed with NRB at flush rate oxygen.

We performed a crossover trial using healthy volunteers. Subjects underwent 3-min trials of preoxygenation with NRB mask at 25 L/min oxygen delivered from a portable tank, NRB at flush rate oxygen from a portable tank, NRB with flush rate oxygen from an onboard ambulance tank, and BVM with flush rate oxygen from an onboard ambulance tank. The primary outcome was the fraction of expired oxygen (FeO₂). We compared the FeO₂ of the BVM-flush to other study groups, using a noninferiority margin of 10%.

We enrolled 30 subjects. Mean FeO₂ values for NRB-25, NRB-flush ambulance, NRB-flush portable, and BVM-flush were 63% (95% confidence interval [CI] 58-68%), 74% (95%, CI 70-78%), 78% (95%, CI 74-83%), and 80% (95%, CI 75-84%), respectively. FeO₂ values for NRB-flush on both portable tank and ambulance oxygen were noninferior to BVM-flush on the ambulance oxygen system (FeO₂ differences of 1%, 95% CI -3% to 6%; and 6%, 95% CI 1-10%). FeO₂ for the NRB-25 group was inferior to BVM-flush (FeO₂ difference 16%, 95% CI 12-21%).

Among healthy volunteers, flush rate preoxygenation using NRB masks is noninferior to BVM using either a portable oxygen tank or ambulance oxygen. This is significant because preoxygenation using NRB masks with flush rate oxygen presents a simpler alternative to the use of BVMs. Preoxygenation using NRB masks at 25 L/min from a portable tank is inferior to BVM at flush rate.