High-flow nasal oxygen used before and during apnoea prolongs time to desaturation at induction of anaesthesia. It is unclear how much oxygenation before apnoea prolongs this time. We randomly allocated 84 participants to 3 minutes of pre-oxygenation by one of three methods: 15 l.min^-1 by facemask; 50 l.min^-1 by high-flow nasal cannulae only; or 50 l.min^-1 by high-flow nasal cannulae plus 15 l.min^-1 by mouthpiece. We then anaesthetised and intubated the trachea of 79 participants and waited for oxygen saturation to fall to 92%. Median (IQR [range]) times to desaturate to 92% after pre-oxygenation with facemask oxygen, high-flow nasal oxygen only and high-flow nasal oxygen with mouthpiece, were: 309 (208-417 [107-544]) s; 344 (250-393 [194-585]) s; and 386 (328-498 [182-852]) s, respectively, p = 0.014. Time to desaturation after facemask pre-oxygenation was shorter than after combined nasal and mouthpiece pre-oxygenation, p = 0.006. We could not statistically distinguish high-flow nasal oxygen without mouthpiece from the other two groups for this outcome. Median (IQR [range]) arterial oxygen partial pressure after 3 minutes of pre-oxygenation by facemask, nasal cannulae and nasal cannulae plus mouthpiece, was: 49 (36-61 [24-66]) kPa; 57 (48-62 [30-69]) kPa; and 61 (55-64 [36-72]) kPa, respectively, p = 0.003. Oxygen partial pressure after 3 minutes of pre-oxygenation with nasal and mouthpiece combination was greater than after facemask pre-oxygenation, p = 0.002, and after high-flow nasal oxygen alone, p = 0.016. We did not reject the null hypothesis for the pairwise comparison of facemask pre-oxygenation and high-flow nasal pre-oxygenation, p = 0.14.

中文翻译：

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面罩预充氧 vs 高流量鼻氧 vs 高流量鼻氧加咬嘴：一项随机对照试验

在呼吸暂停之前和期间使用高流量鼻氧会延长麻醉诱导时的去饱和时间。目前尚不清楚这次呼吸暂停之前的氧合程度。我们通过以下三种方法之一随机分配 84 名参与者进行 3 分钟的预充氧：15 l.min ^-1通过面罩；50 l.min ^{-1 仅}通过高流量鼻插管；或 50 l.min ^-1通过高流量鼻插管加 15 l.min ^-1通过喉舌。然后，我们对 79 名参与者的气管进行了麻醉和插管，并等待氧饱和度降至 92%。使用面罩氧气、仅高流量鼻氧和带咬嘴的高流量鼻氧预充氧后，去饱和度至 92% 的中位数（IQR [范围]）时间为：309 (208-417 [107-544]) s ; 344 (250-393 [194-585]) 秒；和 386 (328-498 [182-852]) s，分别为 p = 0.014。面罩预充氧后的去饱和时间比鼻腔和咬嘴预充氧联合后的时间短，p = 0.006。对于这一结果，我们无法从统计上区分无吸嘴的高流量鼻氧与其他两组。面罩、鼻插管和鼻插管加咬嘴预充氧 3 分钟后的中位（IQR [范围]）动脉氧分压为：49 (36-61 [24-66]) kPa；57 (48-62 [30-69]) kPa；和 61 (55-64 [36-72]) kPa，分别为 p = 0.003。鼻腔和吸嘴组合预充氧 3 分钟后的氧分压大于面罩预充氧后的氧分压，p = 0.002，单独使用高流量鼻氧后，p = 0.016。我们没有拒绝面罩预充氧和高流量鼻预充氧的成对比较的零假设，p = 0.14。