Objective:To evaluate the effect of oxygen supply via the transnasal self-made pharyngeal oxygen catheter on the safe apnea time in pediatric patients undergoing tonsil surgery. Methods:Sixty American Society of Anesthesiologists physical status Ⅰ or Ⅱ patients of either sex, aged 2-6 yr, weighing 10-20 kg, scheduled for elective tonsillectomy under general anesthesia, were divided into 2 groups ( n=30 each) using a random number table method: transnasal self-made pharyngeal oxygen catheter for oxygen supply group (group NO) and control group (group C). Anesthesia was induced with intravenous midazolam, propofol, fentanyl and cis-atracurium, and then ventilation was performed with a mask, and the mask was removed when the exhaled oxygen concentration (C ETO 2) reached more than 90%.In group NO, the self-made oxygen catheter was implanted into the oropharynx through the nose, and the 100% oxygen at 10 L/min was aspirated through the humidification bottle until the intubation was successful.In group C, the transnasal self-made oxygen catheter was not implanted, and the rest of the protocol was similar to those previously described in group NO.The visual laryngoscope was implanted to simulate difficult airways.When SpO 2 ≤ 95% or the safe apnoea time reached 600 s, the observation of apnea was stopped, and mechanical ventilation was started after successful rapid endotracheal intubation.The safe apnea time (from removing the mask until SpO 2 decreased to 95%), value of C ETO 2 at the end of mask ventilation, and the minimum value of SpO 2 after stopping mask ventilation were recorded.Heat rate and mean arterial pressure were observed and recorded on admission to the operating room, immediately after onset of apnea and immediately after successful endotracheal intubation.The SpO 2, P ETCO 2 and cross-sectional area of gastric antrum were also recorded immediately after onset of apnea and immediately after successful endotracheal intubation, and the rate of increase in P ETCO 2 was calculated.The nasal bleeding, nasal dryness, postoperative pharyngeal discomfort and other adverse reactions were recorded when the self-made pharyngeal oxygen catheter was placed. Results:Compared with group C, the safe apnea time was significantly prolonged, the rate of increase in P ETCO 2 was decreased, the minimum value of SpO 2 after stopping mask ventilation was increased, and the heat rate, mean arterial pressure, SpO 2 and P ETCO 2 were increased immediately after successful intubation ( P<0.05), no significant change was found in C ETO 2 after stopping mask ventilation and cross-sectional area of gastric antrum at each time point in group NO ( P>0.05). No adverse reactions such as nasal bleeding, nasal dryness and postoperative pharyngeal discomfort were found when the self-made pharyngeal oxygen catheter was inserted in group NO. Conclusions:The oxygen supply with the transnasal self-made pharyngeal oxygen catheter technique can prolong the safe apnea time in the pediatric patients undergoing tonsil surgery.