Compared with adults, children have higher metabolic needs, and the airway is more likely to collapse. Before tracheal intubation after anesthesia induction, the patient 's spontaneous breathing completely disappears. At this critical stage, the residual oxygen of the lung is consumed, resulting in hypoxemia and atelectasis. Therefore, it is necessary to explore the best oxygenation strategy during intubation. In addition, ultrasound has become a common equipment in the operating room. It has the advantages of portability, repeatability, and no radiation, and can provide strong support for the diagnosis of gastric distension.
Age 2-10 years old;
American Society of Anesthesiologists (ASA) Level I or II;
Children with healthy lungs and hearts;
Clear headed and able to cooperate with anesthesiologists for treatment.
Contraindications for HFNC: (1) Complete obstruction of the upper respiratory tract; (2) Skull base fracture or nasal bone fracture; (3) Patients who refuse to use HFNC;
The American Society of Anesthesiologists (ASA) rating is greater than Level II;
Children with upper respiratory tract infections within 2 weeks;
Pulmonary dysfunction, congenital heart disease in children;
Parallel
high-flow nasal cannula
DeviceIn group H, mask ventilation was performed after the patient lost spontaneous breathing until the end-expiratory oxygen concentration reached 90 %. The lower mask was taken and HFNC was used to record the patient 's safe apnea time.
Apnoea time
Investigators will record the time of oxygen saturation drop to 95 % during intubation.
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