Department of Anaesthesia, University College London NHS Trust, London, UK.
Department of Anaesthesia, University College London NHS Trust, London, UK; University College London, UK.
Int J Obstet Anesth. 2021 Feb;45:28-33. doi: 10.1016/j.ijoa.2020.08.004. Epub 2020 Aug 25.
The role of high flow nasal oxygenation (HFNO) for pre-oxygenation before obstetric general anaesthesia remains unclear. This study aimed to determine the number of vital capacity breaths using HFNO required to pre-oxygenate 90% of parturients to an end-tidal oxygen concentration fraction (FO) of ≥0.90 (termed EN90).
Using up-down, sequential allocation trial design, volunteer term parturients undergoing caesarean delivery were investigated with HFNO with their mouth closed, followed by mouth open, and if FO ≥0.90 was not achieved after a maximum of 20 vital capacity breaths, pre-oxygenation was attempted with a face mask. The primary outcome was the number of vital capacity breaths required using HFNO (mouth open and closed) to achieve EN90. Secondary outcomes included assessment of EN90 using mouth open versus mouth closed and face mask pre-oxygenation, maternal satisfaction and evaluation of fetal cardiotocography.
Twenty women at term were recruited. Successful pre-oxygenation occurred in 4 (20%), 3 (15%) and 14 (70%) women with HFNO mouth closed, HFNO mouth open, and via face mask respectively. At up to 20 vital capacity breaths, face mask pre-oxygenation was more successful at achieving EN90 compared with both HFNO with a closed (P=0.006) or open (P=0.001) mouth. Closed mouth HFNO did not outperform open mouth pre-oxygenation.
Face mask pre-oxygenation is more effective at achieving EN90 compared with to HFNO within a clinically acceptable number of vital capacity breaths. Further studies are needed to determine the role of HFNO in optimising the time before desaturation and for apnoeic oxygenation in term parturients.
高流量鼻氧（HFNO）在产科全身麻醉前预充氧的作用仍不清楚。本研究旨在确定使用 HFNO 进行预充氧，使 90%产妇达到呼气末氧浓度分数（FO）≥0.90（称为 EN90）所需的潮气量呼吸次数。
采用上下序贯分配试验设计，对行剖宫产术的志愿者足月产妇进行研究，采用 HFNO 闭口呼吸，然后开口呼吸，如果最多进行 20 次潮气量呼吸后 FO 仍未达到≥0.90，则尝试用面罩进行预充氧。主要结局是使用 HFNO（闭口和开口）达到 EN90 所需的潮气量呼吸次数。次要结局包括评估开口和闭口 HFNO 以及面罩预充氧时达到 EN90 的情况、产妇满意度和胎儿胎心监护评估。
共招募了 20 名足月产妇。4 名（20%）、3 名（15%）和 14 名（70%）产妇分别通过 HFNO 闭口、HFNO 开口和面罩成功预充氧。在最多 20 次潮气量呼吸时，与 HFNO 闭口（P=0.006）或开口（P=0.001）相比，面罩预充氧在达到 EN90 方面更成功。HFNO 闭口并未优于开口预充氧。
与 HFNO 相比，面罩预充氧在可接受的潮气量呼吸次数内更有效地达到 EN90。需要进一步研究来确定 HFNO 在优化足月产妇缺氧前时间和用于无呼吸氧合方面的作用。
