Flush Rate Oxygen for Emergency Airway Preoxygenation

Recent data suggest that emergency airway preoxygenation with a bag-valve-mask (BVM) device (held with a tight mask seal but without squeezing the bag) is superior to a nonrebreather (NRB) mask at standard oxygen flow rates. We seek to determine whether preoxygenation with an NRB mask with flush rate oxygen (>40 L/min by fully opening a standard oxygen flowmeter) is noninferior to BVM device with standard-flow oxygen (15 L/min). We also seek to compare the efficacy of preoxygenation with NRB mask at flush rate oxygen with both NRB mask with oxygen at 15 L/min and simple mask at flush rate oxygen.

We performed a crossover trial using healthy volunteers. In random sequence, subjects underwent 3-minute trials of preoxygenation with nonrebreather mask with oxygen at 15 L/min (NRB-15), nonrebreather mask with flush rate oxygen (NRB-Flush), BVM device with oxygen at 15 L/min (BVM-15), and simple mask with flush rate oxygen. The primary outcome measure was the FeO₂ in a single exhaled breath. We compared the FeO₂ of NRB-Flush to other study groups, using a prespecified noninferiority margin of 10%.

We enrolled 26 subjects. Mean FeO₂ values for NRB-15, NRB-Flush, BVM-15, and simple mask with flush rate oxygen were 54% (95% confidence interval [CI] 50% to 57%), 86% (95% CI 84% to 88%), 77% (95% CI 74% to 81%), and 72% (95% CI 69% to 76%), respectively. FeO₂ for NRB-Flush was noninferior to BVM-15 (difference 8%; 95% CI 5% to 11%). FeO₂ for NRB-Flush was higher than both NRB-15 (FeO₂ difference 32%; 95% CI 29% to 35%) and simple mask with flush rate oxygen (FeO₂ difference 13%; 95% CI 10% to 17%).

Preoxygenation with NRB-Flush was noninferior to BVM-15. NRB with flush rate oxygen may be a reasonable preoxygenation method for spontaneously breathing patients undergoing emergency airway management.