Can high‐flow nasal oxygen redefine our end‐point for pre‐oxygenation?

Abstract

We read with interest the study by Shippam et al. [1] regarding high-flow humidified nasal oxygen (HFNO) for pre-oxygenation of pregnant women in preparation for general anaesthesia. The findings from this study do not support the use of HFNO to pre-oxygenate term pregnant women. The primary end-point used was an end-tidal oxygen fraction (F ET O 2 ) ≥ 0.9 which is a recommended target for pre-oxygenation by the Obstetric Anaesthetists' Association [2] and the Difficult Airway Society. However, with the advancement in the use of HFNO as an adjunct in both pre-oxygenation and apnoeic oxygenation, should this target be revised? The use of HFNO maximises the physiological phenomenon of aventilatory mass flow, driving oxygen into the lungs and flushing out other dead space gases present [3]. This, coupled with the splinting of upper airways and reduction in associated shunt, can improve oxygenation [3].If this is the case, then is it a prerequisite to preoxygenate to a value of F ET O 2 ≥ 0.9 in a situation where we can continually replenish our oxygen stores via continuous HFNO? If the patency of the airway can be maintained can HNFO redefine our end-point for pre-oxygenation?

Determining the effective pre‐oxygenation interval in obstetric patients using high‐flow nasal oxygen and standard flow rate facemask: a biased‐coin up–down sequential allocation trial

“…Apnoeic oxygenation has shown promise in other patient populations , yet we did not investigate this in the current study due to obvious ethical implications in parturients. Some have suggested that if arterial desaturation could be slowed with high‐flow nasal oxygen following induction, it might not be a prerequisite to pre‐oxygenate to a value of ETO 2 ≥ 90% . Indeed, if a lower pre‐oxygenation endpoint was used (i.e.…”

“…oxygenate to a value of ETO 2 ≥ 90% [22]. Indeed, if a lower pre-oxygenation endpoint was used (i.e.…”

Redefining endpoints with apnoeic oxygenation in pregnancy – better the devil you know than the devil you don't?

“…We thank Tanna and Saha for their interest in our study and for raising a thought‐provoking discussion about the potential for lowering end‐tidal oxygen fraction endpoint in obstetric patients when using high‐flow nasal oxygenation.…”