吸氧去氮的正确操作及其安全隐患的探讨

Implications of inadequate preoxygenation and appropriate management strategies

吸氧去氮也称作预充氧,是指吸入高浓度的氧气,呼出肺内的氮气,最大限度的替代肺内的氮气,从而增加氧储备,目的是延长无通气期安全时限,为气管插管建立人工气道赢得更多的时间。无通气期安全时限是指停止通气后指尖脉搏血氧饱和度(SpO_2)降至90%以下所用的时间。无通气期安全时限判断的依据是氧解离曲线,根据氧解离曲线,血氧分压>60 mm Hg时,血红蛋白氧饱和度>90%,此时血液的携氧能力较好,能为组织提供足够的氧气,不会发生低氧血症。在有效的吸氧去氮前提下,全麻患者可以耐受更长的无通气时间,对于通气困难、插管困难、肥胖、老年人、小儿、肺部疾病等患者有着非常明确的使用价值。

Denitrogenation or preoxygenation is a process that residual nitrogen in the lungs is replaced with oxygen. Preoxygenation increases oxygen reserve before general anesthesia. The main goal of denitrogenation is to extend the duration of non-hypoxic apnea,which is defined as the time elapsed until the Sp O2 reaches below 90%. According to the oxygen dissociation curve,when the oxygen partial pressure in the blood is kept above 60 mm Hg,the hemoglobin oxygen saturation can still stay above 90% and the blood still has high oxygen carrying capacity. This could provide adequate oxygenation for most tissues without hypoxemia. Sufficient preoxygenation provides valuable additional time before induction and extends the safety margin of apnea period. The technique proved particularly critical if mask ventilation or tracheal intubation are difficult. Denitrogenation is important during general anesthesia for neonates,geriatric patients,obese patients or patients with pulmonary system co-morbidities.