After nasotracheal intubation, nitrous oxide 1.5-3L and oxygen 1-2 L were given for about 6-20 minutes, then the flow rates were switched to minimal flow of nitrous oxide 2.8 ml/kg and oxygen 4 ml/kg.

• 在鼻孔插入气管内管后，先给笑 气1.；5-3 L，氧气1-2 L约6-20 min，然后流量降为笑气2