Time to adequate preoxygenation when using flush rate oxygen

Abstract

Objective

Preoxygenation utilizing a non-rebreather mask (NRB) to deliver oxygen at the maximal flow rate (>50 L/min) from a standard hospital gas flowmeter (i.e., the flush rate) is an accepted technique during emergency airway management. Existing guidance to preoxygenate patients for at least 3 min is based on use of oxygen-delivery devices not commonly used in the emergency department (e.g., a closed anesthesia circuit). We sought to determine the median length of time needed to achieve adequate preoxygenation utilizing an NRB with flush rate oxygen.

Methods

Healthy volunteers performing tidal breathing underwent a 5-min trial of preoxygenation with NRB mask with flush rate oxygen. End-tidal oxygen (EtO2), a measure of the degree of adequate preoxygenation, was recorded every 15 s. Adequate preoxygenation was defined as EtO2 ≥ 85 %.

Results

We enrolled 50 participants. The median maximum EtO2 achieved during preoxygenation was 87 % (interquartile range [IQR] 87–89 %) and all participants achieved an EtO2 > 80 %. The median time to reach an EtO2 of 85 % was 90 s (IQR 60–135 s). By 3 min, 86 % (95 % CI 73 % to 94 %) of participants had achieved adequate preoxygenation.

Conclusions

In healthy participants undergoing preoxygenation with an NRB mask with flush rate oxygen, the median time to adequate preoxygenation was 90 s and 86 % were adequately preoxygenated at 3 min. This suggests that 3 min of preoxygenation is a reasonable target using this technique.