This video explains how electromyography endotracheal tubes work during thyroid surgery. Also known as, EMG ET tubes, these are a type of Intraoperative Neuromonitoring (IONM) which serve a big role preventing nerve injury by monitoring recurrent laryngeal nerve activity. Placement of the tube during intubation is important as the surface electrodes should be in contact with the vocal cords. Incorrect placement would render the tube ineffective and could cause damage to the nerve. Both, macintosh and video laryngoscopes can be used if there is poor visibility during intubation.
During surgery the tube may shift from its correct position for several reasons, primarily movement of the neck, so it’s important to check its correct placement throughout the duration of surgery. The tube itself has electrodes located at the tip. These electrodes come into contact with the vocal cords and detect electrical signals produced by the nerves. These signals are transmitted to a monitoring system which allows for continuous monitoring throughout the surgery. Once the EMG ET tube is properly placed, it can detect electrical signals produced by the nerve by using a stimulation probe. Whenever the nerve is stimulated surgeons and anesthesiologists can view the signals on a screen and listen to the sounds produced by pressing directly above the vocal cords.
The EMG signals are transmitted to a real-time monitoring system which helps surgeons view the signals on a screen and evaluate nerve integrity. During surgery this feedback helps surgeons adjust their technique to avoid nerve damage. Stimulation of the nerve creates a sinusoidal wave on the nerve integrity monitor along with an audible signal confirming its intactness. These waveforms, also known as electromyograms. In a normal resting state, should show very little electrical activity. The intensity can be seen by the amplitude of the wave. And the duration can provide information about the speed of muscle activation. A decrease or loss of EMG signals in response to nerve stimulation can indicate nerve damage or irritation.