This study would explore the safety and feasibility of a reversible induction strategy for uncertain difficult airway. This reversible induction strategy would include high flow nasal canular oxygenation support, short-term effect anesthetic including Propofol and Remifentanil for sedation and analgesia and Sugammadex would be used for reverse the muscle relaxant.

Inclusion Criteria:

• >18 years old,<65 years old
• Signed informed consent
• Undergoing selective operation （ time of operation is over two hours）
• ASA classification I-II
• Mallampati classification 3-4
• suspicious difficult airway, but the anesthetists decide to try to rapid induction

Exclusion Criteria:

• Patients with several dysfunctions of liver, kidney or heart)
• Patients with a full stomach or have other risk factors of reflux aspiration
• Any medicine was taken before surgery, which might enhance or mitigate the effects of muscle relaxant
• Infection of the mouth or nose
• Allergy history of any medicine which would be used in this study
• Pregnant and lactating women
• Patients with neuromuscular disease

Patients with an uncertain difficult airway, who will undergo a selective operation and need trachea intubtion.

IPD is unavailable to other researchers