关键词: 喉返神经, 肌电图, 纤支镜, 术中神经监测, 气管内导管, 可视喉镜

Abstract: 【Abstract】 Objective To investigate the optimal depth of endotracheal tube （ETT） which is closely related with the effectiveness of intraoperative neuromonitoring （IONM） for recurrent laryngeal nerve（RLN）during thyroid surgery in order to guarantee the accuracy of IONM for LRN especially when visible intubation devices are not available. Methods This clinical study involved two phases. In phase 1 study, 133 patients whose heights ranging from 145 cm to 180 cm were enrolled. Height and body weight were recorded；video intubation devices were utilized for intubation and observation；while the midline of the probe reaching the vocal cords opening level, the depth of ETT（Optimal depth） was also recorded and corresponding mean values for male and female were calculated separately. In phase 2 study, 35 patients with same inclusion criteria as in phase 1 study were intubated without any visible intubation devices and the ETTs were fixed in male or female to the depth according to the mean values of optimal depth obtained from phase 1 study, respectively；the success rate of electromyography （EMG） for laryngeal recurrent nerve monitoring was examined and compared to that in phase 1 study. Results Based on this certain study sample, the optimal depth of ETT in IONM for RLN shows positive correlation with patient height, the mean values are 21.7 cm and 19.7 cm in male and female, respectively. Fixing the ETT to the mean value of optimal depth either in male or in female can provide similar success rate of IONM for RLN when compared to direct localization with visible intubation devices. Conclusion In certain population，the mean value of optimal depth of ETT in IONM for RLN is 21.7 cm for male while 19.7 cm for female，one may fix the ETT to this mean value to achieve effective and satisfied IONM without the help of visible intubation devices.

Key words: EMG, IONM, Video laryngoscope, Endotracheal tube, RLN, Fiberscope