Background

Hypoxaemia during general anaesthesia can cause harm. Apnoeic oxygenation extends safe apnoea time, reducing risk during airway management. We hypothesised that low-flow nasal oxygenation (LFNO) would extend safe apnoea time similarly to high-flow nasal oxygenation (HFNO), whilst allowing face-mask preoxygenation and rescue.

Methods

A high-fidelity, computational, physiological model was used to examine the progression of hypoxaemia during apnoea in virtual models of pregnant women in and out of labour, with BMI of 24–50 kg m⁻². Subjects were preoxygenated with oxygen 100% to reach end-tidal oxygen fraction (FE'O₂) of 60%, 70%, 80%, or 90%. When apnoea started, HFNO or LFNO was commenced. To simulate varying degrees of effectiveness of LFNO, periglottic oxygen fraction (FgO₂) of 21%, 60%, or 100% was configured. HFNO provided FgO₂ 100% and oscillating positive pharyngeal pressure.

Results

Application of LFNO (FgO₂ 100%) after optimal preoxygenation (FE'O₂ 90%) resulted in similar or longer safe apnoea times than HFNO FE'O₂ 80% in all subjects in labour. For BMI of 24, the time to reach SaO₂ 90% with LFNO was 25.4 min (FE'O₂ 90%/FgO₂ 100%) vs 25.4 min with HFNO (FE'O₂ 80%). For BMI of 50, the time was 9.9 min with LFNO (FE'O₂ 90%/FgO₂ 100%) vs 4.3 min with HFNO (FE'O₂ 80%). A similar finding was seen in subjects with BMI ≥40 kg m⁻² not in labour.

Conclusions

There is likely to be clinical benefit to using LFNO, given that LFNO and HFNO extend safe apnoea time similarly, particularly when BMI ≥40 kg m⁻². Additional benefits to LFNO include the facilitation of rescue face-mask ventilation and ability to monitor FE'O₂ during preoxygenation.

中文翻译：

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足月妊娠受试者窒息吸氧技术的比较：计算模型研究

背景

全身麻醉期间的低氧血症会造成伤害。呼吸暂停氧合可延长安全呼吸暂停时间，降低气道管理期间的风险。我们假设低流量鼻氧合 (LFNO) 会像高流量鼻氧合 (HFNO) 一样延长安全呼吸暂停时间，同时允许面罩预氧合和抢救。

方法

^{在 BMI 为 24-50 kg m -2}的孕妇虚拟模型中，使用高保真计算生理模型检查呼吸暂停期间低氧血症的进展。受试者使用 100% 的氧气进行预充氧，以达到60%、70%、80% 或 90%的潮气末氧分数 (FE'O _{2 )。}当呼吸暂停开始时，HFNO 或 LFNO 开始。为了模拟 LFNO 的不同程度的有效性，配置了 21%、60% 或 100%的声门周氧分数 (FgO _{2 )。}HFNO 提供 100% 的 FgO ₂和振荡的咽正压。

结果

_{在最佳预氧合 (FE'O 2} 90%) 后应用 LFNO (FgO ₂ 100% ) 导致所有分娩对象的安全呼吸暂停时间与 HFNO FE'O ₂ 80% 相似或更长。对于 24 的 BMI，使用 LFNO 时达到SaO ₂ 90% 的时间为 25.4 分钟（FE'O ₂ 90%/FgO ₂ 100%） ，而使用HFNO时为25.4 分钟（FE'O ₂ 80%）。对于 50 的 BMI，使用 LFNO (FE'O ₂ 90%/FgO ₂ 100%)的时间为 9.9 分钟，而使用 HFNO (FE'O _{2 80%) 的时间}为4.3 分钟。^{在 BMI ≥ 40 kg m -2}未分娩的受试者中也观察到类似的发现。

结论

^{考虑到 LFNO 和 HFNO 延长安全呼吸暂停时间的方式相似，特别是当 BMI ≥ 40 kg m -2}时，使用 LFNO 可能具有临床益处。LFNO 的其他好处包括促进救援面罩通气和在预充氧期间监测 FE'O ₂的能力。