Preparation of SaCoVLM
The SaCoVLM includes a visual channel, a intubation channel, a gastric tube channel, a camera and connecting wires. The camera is fixed on the right side of ventral cuff,connected with the screen and inserted into the visual channel. During placement, the SaCoVLM is adjusted according to the image displayed on the screen. A recharged battery is used to provide energy. The camera was inserted into the visual channel and connected with the screen before later use. Initial size selection for the SaCoVLM was as follows: size 2.5 for patients 20–30 kg and size 3 for those 30–50 kg. However, in the pre-experimental process, it was found that size 3 laryngeal mask is too large for 30 kg children because it is difficult to insert the device under direct vision. Therefore, in the formal experiment process, we selected size 2.5 for 20-35 kg and size 3 for 35 kg–50 kg children.Routinely check the cuff of the laryngeal mask before anesthesia induction. Use lidocaine gel to fully lubricate the back of the laryngeal mask, the inner wall of the airway tube of the laryngeal mask and the outer wall of the tracheal tube, and evacuate the cuff for use. Check the light source and clarity of the flexible intubation scope (FIS), and lubricate the stem of the flexible intubation scope.