Time to adequate preoxygenation when using flush rate oxygen

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.

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 %.

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.

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.