Clin Exp Otorhinolaryngol.  2020 Aug;13(3):291-298. 10.21053/ceo.2019.01249.

Application of Novel Intraoperative Neuromonitoring System Using an Endotracheal Tube With Pressure Sensor during Thyroid Surgery: A Porcine Model Study

• Sung ES
• Shin SC
• Kwon HK
• Kim J
• Park DH
• Choi SW
• Kim SH
• Lee JC
• Ro JH
• Lee BJ

• KMID: 2504925
• DOI: http://doi.org/10.21053/ceo.2019.01249

Abstract

Objectives
. The loss of signal during intraoperative neuromonitoring (IONM) using electromyography (EMG) in thyroidectomy is one of the biggest problems. We have developed a novel IONM system with an endotracheal tube (ETT) with an attached pressure sensor instead of EMG to detect laryngeal twitching. The aim of the present study was to investigate the feasibility and reliability of this novel IONM system using an ETT with pressure sensor during thyroidectomy in a porcine model.
Methods
. We developed an ETT-attached pressure sensor that uses the piezoelectric effect to measure laryngeal muscle twitching. Stimulus thresholds, amplitude, and latency of laryngeal twitching evaluated using the pressure sensor were compared to those measured using transcartilage needle EMG. The measured amplitude changes by EMG and the pressure sensor during recurrent laryngeal nerve (RLN) traction injury were compared.
Results
. No significant differences in stimulus threshold intensity between EMG and the pressure sensor were observed. The EMG amplitude detected at 0.3 mA, increased with increasing stimulus intensity. When the stimulus was more than 1.0 mA, the amplitude showed a plateau. In a RLN traction injury experiment, the EMG amplitude did not recover even 20 minutes after stopping RLN traction. However, the pressure sensor showed a mostly recovery.
Conclusion
. The change in amplitude due to stimulation of the pressure sensor showed a pattern similar to EMG. Pressure sensors can be feasibly and reliably used for RLN traction injury prediction, RLN identification, and preservation through the detection of laryngeal muscle twitching. Our novel IONM system that uses an ETT with an attached pressure sensor to measure the change of surface pressure can be an alternative to EMG in the future.

Keyword

Intraoperative Neurophysiological Monitoring; Pressure Sensor; Electromyography; Recurrent Laryngeal Nerve; Thyroidectomy

Figure

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  Fig. 1. (A) Novel device and surgical field. Photograph of an endotracheal tube with attached pressure sensor. (B) Photograph of the surgical field on the pig, demonstrating recurrent laryngeal nerve (RLN) traction injury. Transcartilage needle electrodes were inserted into the vocal cord level of both sides of the thyroid cartilage. The automatic periodic stimulation (APS) was placed on the vagus nerve, left under continuous intermittent intraoperative neuromonitoring, and the left RLN was pulled up using silk 3-0. White arrow, electromyography electrodes; Black arrow, APS.

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  Fig. 2. Electromyography (EMG) and endotracheal tube with pressure sensor recordings, showing the amplitude and latency of EMG and the pressure sensor for 1 mA stimulation using the Nerve Integrity Monitor 3.0 system in pig. Upper graph, pressure sensor signal; Lower graph, EMG signal.

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  Fig. 3. Change in electromyography (EMG) and pressure sensor according to stimulus. The amplitudes of EMG (A) and the pressure sensor (B) of the vocalis muscle depending on stimulus level.

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  Fig. 4. Continuous amplitude changes of electromyography (EMG) and pressure sensor before recurrent laryngeal nerve (RLN) traction (A), when RLN traction stopped (B), and 20 minutes after RLN traction (C) for 3-mA stimulation using the Nerve Integrity Monitor 3.0 system in pigs. Upper graph, pressure sensor signal; Lower graph, EMG signal.

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  Fig. 5. Amplitude (%) patterns of electromyography (EMG, dotted line) and the pressure sensor (solid line) change depending on the time of the recurrent laryngeal nerve (RLN) traction injury: before RLN traction (a), when RLN traction stopped (b), and 20 minutes after RLN traction (c). a vs. b: P<0.001, b vs. c: P=0.001, a vs. c: P=0.221 in pressure sensor; a vs. b: P<0.001, b vs. c: P=0.044, a vs. c: P<0.001 in EMG. ETT, endotracheal tube.

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