Impact of positional changes in neural monitoring endotracheal tube on amplitude and latency of electromyographic response in monitored thyroid surgery: Results from the Porcine Experiment

Background. The purpose of this study was to evaluate electromyography (EMG) amplitude and latency changes during tube dislocation in monitored thyroid surgery, which may be observed without recurrent laryngeal nerve injury. Methods. Duroc-Landrace piglets were intubated with the TriVantage EMG tube. We measured EMG changes during both upward and downward tube dislocation (10-20 mm) and rotation (45-90 degrees) with continuous neuromonitoring. Results. The EMG amplitude varied significantly with induced endotracheal tube rotation and depth changes. However, the EMG latency was relatively unaffected by such tube dislocation, just a transient artifactual latency change was observed in the situation of extreme amplitude variation. Conclusion. Amplitude changes without latency changes may be due to changes in tube position alone during surgery, but could still reflect a neurophysiologic event; amplitude changes during neuropraxic injury merit additional investigation. Thus, the combined event (concordant amplitude decrease and latency increase) serves as an appropriate adverse EMG event correlating with impending neural injury. (c) 2015 Wiley Periodicals, Inc.