Background

During induction of general anaesthesia, patients frequently experience apnoea, which can lead to dangerous hypoxaemia. An obstructed upper airway can impede attempts to provide ventilation. Although unrelieved apnoea is rare, it continues to cause deaths. Clinical investigation of management strategies for such scenarios is effectively impossible because of ethical and practical considerations.

Methods

A population-representative cohort of 100 virtual (in silico) subjects was configured using a high-fidelity computational model of the pulmonary and cardiovascular systems. Each subject breathed 100% oxygen for 3 min and then became apnoeic, with an obstructed upper airway, during induction of general anaesthesia. Apnoea continued throughout the protocol. When arterial oxygen saturation (Sao₂) reached 20%, 40%, or 60%, airway obstruction was relieved. We examined the effect of varying supraglottic oxygen fraction (Fo₂) on the degree of passive re-oxygenation occurring without tidal ventilation.

Results

Relief of airway obstruction during apnoea produced a single, passive inhalation (caused by intrathoracic hypobaric pressure) in all cases. The degree of re-oxygenation after airway opening was markedly influenced by the supraglottic Fo₂, with a supraglottic Fo₂ of 100% providing significant and sustained re-oxygenation (post-rescue Pao₂ 42.3 [4.4] kPa, when the airway rescue occurred after desaturation to Sao₂ 60%).

Conclusions

Supraglottic oxygen supplementation before relieving upper airway obstruction improves the effectiveness of simulated airway rescue. Management strategies should be implemented to assure a substantially increased pharyngeal Fo₂ during difficult airway management.

中文翻译：

---

氧气含量对气道抢救的影响：计算模型研究。

背景

在全身麻醉诱导期间，患者经常会出现呼吸暂停，这可能导致危险的低氧血症。上呼吸道阻塞会阻碍提供通气的尝试。尽管缓解呼吸暂停的情况很少见，但仍继续导致死亡。出于道德和实践考虑，实际上不可能进行针对此类情况的管理策略的临床研究。

方法

使用肺和心血管系统的高保真计算模型配置了100个虚拟（计算机）受试者的人口代表性队列。在全身麻醉的诱导过程中，每位受试者呼吸100％的氧气3分钟，然后变为上呼吸道阻塞的气喘病。在整个方案中呼吸暂停继续进行。当动脉血氧饱和度（S a o ₂）达到20％，40％或60％时，气道阻塞得以缓解。我们研究了在没有潮气通气的情况下改变声门上氧分数（F o ₂）对被动再充氧程度的影响。

结果

在所有情况下，呼吸暂停期间气道阻塞的缓解均产生了一次被动的吸入（由胸腔内低压引起）。声门上F o ₂对气道开放后的再氧化程度有显着影响，声门上F o ₂为100％，可提供显着且持续的再氧合（救援后P a o ₂ 42.3 [4.4] kPa，当去饱和度达到S a o ₂ 60％后进行气道抢救。

结论

缓解上呼吸道阻塞之前的声门上补氧提高了模拟气道抢救的有效性。管理战略应被实现以确保显着提高的咽˚F Ò ₂期间困难气道管理。