Determining the Optimal Position of Surface Electrodes for Diaphragm Electromyography: A Cross-Sectional Study.

BACKGROUND: Placing electrodes on different aspects of the chest determines the motor firing from the diaphragm. The electrode placement close to the extent of the muscle gave promising readings as compared to the ones that were placed away. The position with the maximum amplitude and least duration was chosen. Positions of the electrodes were decided as per the extent of the muscle. The aim is to determine the appropriate position of surface electrodes for surface diaphragm electromyography (EMG). MATERIAL AND METHODOLOGY: Thirty healthy individuals of age ranging from 21 to 45 years were included in the study. Participants were made to lie down in a supine position and different positions like G1 (recording electrode) 5 cm superior to the tip of the xiphoid process and G2 (reference) 16 cm along the costal margin from G1, G1 over the xiphoid tip and G2 at the seventh intercostal space at the costochondral junction and G1 over the xiphoid tip and G2 at the eight intercostal space at the costochondral junction were used for assessing maximum amplitudes and durations were observed by using a Octopus New Wave EMG machine (Octopus Medical Technologies, Vadodara, IND). After observing all the positions, an optimum position for maximum amplitude and least duration was analyzed. RESULTS: As per the study, out of the four positions, the electrode placements on the tip of the xiphoid process and 16 cm away diagonally on the sixth intercostal space showed maximum amplitude and the least duration with maximum mean amplitude and less mean duration of 232.35 and 7.316. On the seventh intercostal space it was 199.15 and 7.887 and on the eighth intercostal space was 176.055 and 8.639. The tip of the xiphoid process and 16 cm away diagonally on the sixth intercostal space is chosen as the appropriate position for electrode placement for EMG of the diaphragm. CONCLUSION: We conclude that the best electrode position was when the electrodes were placed 5 cm superior to the xiphoid process, i.e., G1, and 16 cm away from the recording electrode on the costochondral junction, i.e., G2, at the sixth intercostal space. Ground electrode placement is the nearest bony prominence, i.e., xiphisternum.

Noninvasive monitoring of the vagus nerve during thyroid surgery using cutaneous adhesive and needle electrodes: What is the optimal configuration?

OBJECTIVE: Endotracheal tube (ETT) surface electrodes are used to monitor the vagus nerve (VN), recurrent laryngeal nerve (RLN), and external branch of the superior laryngeal nerve (EBSLN) during thyroid and parathyroid surgery. Alternative nerve monitoring methods are desirable when intubation under general anesthesia is not desirable or possible. In this pilot study, we compared the performance of standard ETT electrodes to four different noninvasive cutaneous recording electrode types (two adhesive electrodes and two needle electrodes) in three different orientations. METHODS: The VN was stimulated directly during thyroid and parathyroid surgery using a Prass stimulator probe. Electromyographic (EMG) responses for each patient were recorded using an ETT plus one of the following four cutaneous electrode types: large-foot adhesive, small-foot adhesive, long-needle and short-needle. Each of the four electrode types was placed in three orientations: (1) bilateral, (2) ipsilateral mediolateral, and (3) ipsilateral craniocaudal. RESULTS: Four surgical cases were utilized for data collection with the repetitive measures obtained in each subject. Bilateral electrode orientation was superior to ipsilateral craniocaudal and ipsilateral mediolateral orientations. Regardless of electrodes type, all amplitudes in the bilateral orientation were >100 µV. When placed bilaterally, the small-foot adhesive and the long-needle electrodes obtained the highest EMG amplitudes as a percentage of ETT amplitudes. CONCLUSION: Cutaneous electrodes could potentially be used to monitor the VN during thyroid and parathyroid procedures. Different electrode types vary in their ability to record amplitudes and latencies. Bilateral orientation improves EMG responses in all electrode types. Additional validation of cutaneous electrodes as an alternative noninvasive method to monitor the VN is needed.

Fabrication and Characterization of a Flexible Thin-Film-Based Array of Microelectrodes for Corneal Electrical Stimulation.

The electric stimulation (ES) of the cornea is a novel therapeutic approach to the treatment of degenerative visual diseases. Currently, ES is delivered by placing a mono-element electrode on the surface of the cornea that uniformly stimulates the eye along the electrode site. It has been reported that a certain degree of correlation exists between the location of the stimulated retinal area and the position of the electrode. Therefore, in this study, we present the development of a sectioned surface electrode for selective electric stimulation of the human cornea. The proposed device consists of 16 independent microelectrodes, a reference electrode, and 18 contact pads. The microelectrodes have a size of 200 µm × 200 µm, are arranged in a 4 × 4 matrix, and cover a total stimulation area of 16 mm2. The proposed fabrication process, based on surface micromachining technology and flexible electronics, uses only three materials: polyimide, aluminum, and titanium, which allow us to obtain a simplified, ergonomic, and reproducible fabrication process. The fabricated prototype was validated to laboratory level by electrical and electrochemical tests, showing a relatively high electrical conductivity and average impedance from 712 kΩ to 1.4 MΩ at the clinically relevant frequency range (from 11 Hz to 30 Hz). Additionally, the biocompatibility of the electrode prototype was demonstrated by performing in vivo tests and by analyzing the polyimide films using Fourier transform infrared spectroscopy (FTIR). The resulting electrode prototype is robust, mechanically flexible, and biocompatible, with a high potential to be used for selective ES of the cornea.

Evaluation method of motor unit number index based on optimal muscle strength combination.

Repeatability is an important attribute of motor unit number index (MUNIX) technology. This paper proposes an optimal contraction force combination for MUNIX calculation in an effort to improve the repeatability of this technology. In this study, the surface electromyography (EMG) signals of the biceps brachii muscle of eight healthy subjects were initially recorded with high-density surface electrodes, and the contraction strength was the maximum voluntary contraction force of nine progressive levels. Then, by traversing and comparing the repeatability of MUNIX under various combinations of contraction force, the optimal combination of muscle strength is determined. Finally, calculate MUNIX using the high-density optimal muscle strength weighted average method. The correlation coefficient and the coefficient of variation are utilized to assess repeatability. The results show that when the muscle strength combination is 10, 20, 50 and 70% of the maximum voluntary contraction force, the repeatability of MUNIX is greatest, and the correlation between MUNIX calculated using this combination of muscle strength and conventional methods is high (PCC > 0.99), the repeatability of the MUNIX method improved by 11.5-23.8%. The results indicate that the repeatability of MUNIX differs for various combinations of muscle strength and that MUNIX, which is measured with a smaller number and lower-level contractility, has greater repeatability.

Feasibility of facial nerve monitoring using adhesive surface electrodes during parotidectomy: a comparative study with needle electrodes.

PURPOSE: Electrophysiological monitoring of the facial nerve during parotidectomy has been reported as an adjunctive method to prevent facial nerve injury. Classically, a needle electrode is used to obtain electromyographic (EMG) signals from facial muscles during facial nerve monitoring (FNM) of parotid surgery, likewise adhesive surface electrodes. This study aimed to investigate the feasibility of performing FNM with surface electrodes during parotid surgery and to compare EMG values with needle electrodes. METHODS: Thirty patients who underwent parotidectomy under FNM using adhesive surface and needle electrodes were included. Two pairs of adhesive surface electrodes and needle electrodes were used for FNM during parotid surgery. Mean amplitudes were collected after electrical facial nerve stimulation at 1 mA after specimen removal. RESULTS: The mean amplitude of the adhesive surface electrodes was 226.50 ± 118.44 µV (orbicularis oculi muscle) and 469.6 ± 306.06 µV (orbicularis oris muscle), respectively. The mean amplitude of the needle electrodes was 449.85 ± 248.10 µV (orbicularis oculi muscle) and 654.66 ± 395.71 µV (orbicularis oris muscle), respectively. The mean amplitude of the orbicularis oris muscle was significantly greater than that of the orbicularis oculi. The amplitude values measured in the orbicularis oculi muscle showed significant differences between the needle and skin electrodes. CONCLUSIONS: Facial nerve monitoring (FNM) using adhesive surface electrodes is feasible in parotid surgery. Although the mean amplitude value of the surface electrode was relatively lower than that of the needle electrode, the surface electrode is considered a feasible and safe EMG recording device for FNM in parotid surgery.

Teaching Essential EMG Theory to Kinesiologists and Physical Therapists Using Analogies Visual Descriptions, and Qualitative Analysis of Biophysical Concepts.

Electromyography (EMG) is a multidisciplinary field that brings together allied health (kinesiology and physical therapy) and the engineering sciences (biomedical and electrical). Since the physical sciences are used in the measurement of a biological process, the presentation of the theoretical foundations of EMG is most conveniently conducted using math and physics. However, given the multidisciplinary nature of EMG, a course will most likely include students from diverse backgrounds, with varying levels of math and physics. This is a pedagogical paper that outlines an approach for teaching foundational concepts in EMG to kinesiologists and physical therapists that uses a combination of analogies, visual descriptions, and qualitative analysis of biophysical concepts to develop an intuitive understanding for those who are new to surface EMG. The approach focuses on muscle fiber action potentials (MFAPs), motor unit action potentials (MUAPs), and compound muscle action potentials (CMAPs) because changes in these waveforms are much easier to identify and describe in comparison to the surface EMG interference pattern (IP).

Numerical Study on Hydrodynamic Characteristics and Electrochemical Performance of Alkaline Water Electrolyzer by Micro-Nano Surface Electrode.

This study constructed a two-dimensional alkaline water electrolyzer model based on the two-phase flow Euler-Euler model. In the model, the micro-nano surface electrodes with different structure types and graphic parameters (distance, height, and width) were used and compared with the vertical flat electrode to evaluate their influence on electrolysis performance. The simulation results show that the performance of the micro-nano surface electrode is much better than that of the vertical flat electrode. The total length of micro-nano structural units relates to the contact area between the electrode and the electrolyte and affects the cell voltage, overpotential, and void fraction. When rectangular structural units with a distance, height, and width of 0.5 µm, 0.5 µm, and 1 µm are used, the total length of the corresponding micro-nano surface electrode is three times that of the vertical flat electrode, and the cathode overpotential decreases by 65.31% and the void fraction increases by 54.53% when it replaces the vertical flat electrode.

Monte Carlo simulations of two-component Coulomb gases applied in surface electrodes.

In this work, we study the gapped surface electrode (SE), a planar system composed of two-conductor flat regions at different potentials with a gapGbetween both sheets. The computation of the electric field and the surface charge density requires solving Laplace's equation subjected to Dirichlet conditions (on the electrodes) and Neumann boundary conditions over the gap. In this document, the gapless surface electrode is modeled as a two-dimensional classical Coulomb gas having punctual charges +qand -qon the inner and outer electrodes, respectively, interacting with an inverse power law 1/r-potential. The coupling parameter Γ between particles inversely depends on temperature and is proportional toq2. Precisely, the density charge arises from the equilibrium states via Monte Carlo (MC) simulations. We focus on the coupling and the gap geometry effect. Mainly on the distribution of particles in the circular and the harmonically-deformed gapped SE. MC simulations differ from electrostatics in the strong coupling regime. The electrostatic approximation and the MC simulations agree in the weak coupling regime where the system behaves as two interacting ionic fluids. That means that temperature is crucial in finite-size versions of the gapped SE where the density charge cannot be assumed fully continuous as the coupling among particles increases. Numerical comparisons are addressed against analytical descriptions based on an electric vector potential approach, finding good agreement.

Materials for Implantable Surface Electrode Arrays: Current Status and Future Directions.

Surface electrode arrays are mainly fabricated from rigid or elastic materials, and precisely manipulated ductile metal films, which offer limited stretchability. However, the living tissues to which they are applied are nonlinear viscoelastic materials, which can undergo significant mechanical deformation in dynamic biological environments. Further, the same arrays and compositions are often repurposed for vastly different tissues rather than optimizing the materials and mechanical properties of the implant for the target application. By first characterizing the desired biological environment, and then designing a technology for a particular organ, surface electrode arrays may be more conformable, and offer better interfaces to tissues while causing less damage. Here, the various materials used in each component of a surface electrode array are first reviewed, and then electrically active implants in three specific biological systems, the nervous system, the muscular system, and skin, are described. Finally, the fabrication of next-generation surface arrays that overcome current limitations is discussed.

Brachialis Muscle Activity Can Be Measured With Surface Electromyography: A Comparative Study Using Surface and Fine-Wire Electrodes.

Muscle activities of the elbow flexors, especially the brachialis muscle (BR), have been measured with intramuscular electromyography (EMG) using the fine-wire electrodes. It remains unclear whether BR activity can be assessed using surface EMG. The purpose of this study was to compare the EMG patterns of the BR activity recorded during elbow flexion using surface and fine-wire electrodes and to determine whether surface EMG can accurately measure the BR activity. Six healthy men were asked to perform two tasks-a maximum isometric voluntary contractions (MVICs) task and an isotonic elbow-flexion task without lifting any weight. The surface and intramuscular EMG were simultaneously recorded from the BR and the long and short heads of the biceps brachii muscle (BBLH and BBSH, respectively). The locations of the muscles were identified and marked under ultrasonographic guidance. The peak cross-correlation coefficients between the EMG signals during the MVICs task were calculated. For the isotonic elbow-flexion task, the EMG patterns for activities of each muscle were compared between the surface and the fine-wire electrodes. All cross-correlation coefficients between the surface EMG signals from the muscles were lower than 0.3. Furthermore, the EMG patterns of the BR activity were not significantly different between the surface and the fine-wire electrodes. The BR has different EMG pattern from the BBLH and the BBSH. The BR activity, conventionally measured with intramuscular EMG, can be accurately accessed with surface EMG during elbow flexion performed without lifting any weight, independent from the BBLH and BBSH activities.

Feasibility of using surface electromyography for the detection of abnormal muscle response in patients with hemifacial spasm / 西安交通大学学报(医学版)

【Objective】 To investigate the feasibility of using surface electromyography （SEMG） for the detection of abnormal muscle response （AMR） in patients with hemifacial spasm （HFS）. 【Methods】 We retrospectively reviewed the clinical data of HFS patients who underwent microvascular decompression （MVD） in our hospital between June 2019 and December 2020. Patients who received both surface electrode （preoperative） and needle electrode （intraoperative） detection of AMR were included. SEMG recorded from two stimulation-recording sites， namely， zygomatic-mentalis and mandibular marginal-orbicularis oculi， was selected for analyzing the characteristics of AMR. The positive rates of AMR detected by these two kinds of electrodes were comprehensively compared. 【Results】 Totally 77 patients were included in this study. When detected with surface electrodes， the positive rate， latency and amplitude of AMR recorded at zygomatic-mentalis oculi were 90.9% （70/77）， （10.87±1.86） ms and （202.8±47.4） μV， and at mandibular marginal-orbicularis oculi were 92.2% （71/77）， （10.41±1.83） ms and （211.1±54.1） μV， respectively. AMR was detected in 74 patients （96.1%） with surface electrodes. There was no significant difference in positive rate， latency and amplitude of AMR between these two stimulation-recording methods. When detected with needle electrodes， the positive rate of AMR recorded at zygomatic-mentalis oculi was 98.7% （76/77）， which was significantly higher than the rate 89.6% （69/77） recorded at mandibular marginal-orbicularis oculi （P=0.016）. The latency and amplitude of AMR recorded at zygomatic-mentalis were （10.63±1.39） ms and （83.5±27.2） μV， and at mandibular marginal-orbicularis oculi were （10.31±1.18） ms and （58.6±21.4） μV. There was no significant difference in latency between the two stimulation-recording methods， but the amplitude recorded at mandibular marginal-orbicularis oculi was significantly lower （P=0.041）. AMR was detected in 76 patients （98.7%） with needle electrodes. There was no significant difference in the detection rate of AMR between surface electrodes and needle electrodes （P=0.500）， the results were moderately consistent （Kappa=0.490， P<0.001）. 【Conclusion】 The detection efficiency of surface electrodes for AMR is similar to that of needle electrode. With its non-invasive characteristic， the surface electrode can be routinely used for electrophysiological evaluation of HFS.

Mediating different-diameter Aß nerve fibers using a biomimetic 3D TENS computational model.

BACKGROUND: Significant progress has been made over the last 50 years in the design, development and testing of transcutaneous electrical nerve stimulation (TENS) in mediating different levels of tactile sensations. However, without knowing how best to stimulate the nerve fibers, the elicited sensation quality will always remain poor and unnatural. NEW METHOD: A new biomimetic 3D TENS computational model is developed to quantify the neural activation mechanism with varied surface electrodes. This model includes seven-layered anatomical structure of the forearm and biophysically-detailed myelinated Aß fibers. The Aß-fiber diameters from 1.5 - 7.5 µm were randomly distributed beneath the skin to mimic the physiologically-realistic fiber population. The arithmetic averaging algorithm and Gaussian filter were adopted to identify the sensation center and to quantify sensation intensities under different stimulation conditions. RESULTS: Fibers larger than 4.5 µm can usually be activated producing tactile sensations such as light touch, pressure, buzz, and vibration. While, fibers with diameters of 3.5 and 3 µm can only be excited at uncomfortable numb and pain sensations. The resulted modelling predictions match the recent psychophysical experimental data. COMPARISON WITH EXISTING METHOD(S): The new TENS model is more physiologically-realistic by introducing a detailed morphological information and key ionic mechanisms in nerve fibers. CONCLUSIONS: Our results indicate that TENS may be a promising method to target functionally-distinct neural pathways in an effort to improve the elicited tactile sensations quality with electrical stimulation. This work provides a promising platform of discovering neural mechanisms under TENS.

Dry Electrodes for Human Bioelectrical Signal Monitoring.

Bioelectrical or electrophysiological signals generated by living cells or tissues during daily physiological activities are closely related to the state of the body and organ functions, and therefore are widely used in clinical diagnosis, health monitoring, intelligent control and human-computer interaction. Ag/AgCl electrodes with wet conductive gels are widely used to pick up these bioelectrical signals using electrodes and record them in the form of electroencephalograms, electrocardiograms, electromyography, electrooculograms, etc. However, the inconvenience, instability and infection problems resulting from the use of gel with Ag/AgCl wet electrodes can't meet the needs of long-term signal acquisition, especially in wearable applications. Hence, focus has shifted toward the study of dry electrodes that can work without gels or adhesives. In this paper, a retrospective overview of the development of dry electrodes used for monitoring bioelectrical signals is provided, including the sensing principles, material selection, device preparation, and measurement performance. In addition, the challenges regarding the limitations of materials, fabrication technologies and wearable performance of dry electrodes are discussed. Finally, the development obstacles and application advantages of different dry electrodes are analyzed to make a comparison and reveal research directions for future studies.

Analysis of the myoelectric characteristics of genioglossus in REM sleep and its improvement by CPAP treatment in OSA patients.

OBJECTIVES: To reveal the characteristics of genioglossus (GG) activation in moderate and severe obstructive sleep apnea (OSA) patients during rapid eye movement (REM) sleep compared with non-rapid eye movement (NREM) sleep and to determine whether continuous positive airway pressure (CPAP) could improve GG activation in OSA patients during sleep. METHODS: All subjects underwent polysomnography (PSG) with synchronous GG electromyography (GGEMG) recording with intra-oral surface electrodes at baseline on the first night. Only those subjects diagnosed with moderate and severe OSA were included and were manually titrated with CPAP to achieve a therapeutic pressure (Pt) with GGEMG recording on the second night. RESULTS: Nine OSA patients and six normal controls were analyzed in this study. The tonic GGEMG was higher in OSA patients during wakefulness (p = 0.003) and NREM sleep (p = 0.015), but it was not higher in REM sleep (p = 0.862). The average phasic activity of OSA patients was significantly higher in all stages, including wakefulness (p = 0.007), NREM sleep (p = 0.005), and REM sleep (p = 0.021). The peak phasic GGEMG was not different in wakefulness compared with normal controls (p = 0.240), but it was higher in OSA patients in NREM sleep (p = 0.001) and REM sleep (p = 0.021), and it was significantly reduced by using CPAP during sleep (NREM sleep: p = 0.027; REM sleep: p = 0.001). CONCLUSIONS: Our results demonstrate that GG activation during NREM and REM sleep is associated with component differences. The tonic component of GGEMG exhibited less of a compensatory increase compared with the phasic component in REM sleep, suggesting that it may be one of the pathological mechanisms of UA collapsibility in REM sleep. In addition, treatment with CPAP can normalize GGEMG activity and mostly reduced the peak phasic GGEMG during sleep.

Feasibility of Intraoperative Neuromonitoring During Thyroid Surgery Using Transcartilage Surface Recording Electrodes.

BACKGROUND: Intraoperative neural monitoring (IONM) has gained widespread acceptance as an adjunct to the gold standard of visual identification of the recurrent laryngeal nerve (RLN) during thyroid surgery. Currently, laryngeal electromyography (EMG) recording during IONM is almost always performed using endotracheal tube (ETT) surface electrodes placed adjacent to vocal folds originating from the inner surface of the thyroid cartilage (TC). Therefore, it was hypothesized that surface recording electrodes placed on the outer surface of the TC should enable access to the EMG response of the vocal folds during IONM. The aim of this experimental study was to evaluate the feasibility of the transcartilage approach for laryngeal EMG recording during IONM. METHODS: A porcine model (12 pigs and 24 RLN sides) with well established applicability in IONM research was used for the experiments. Both ETT electrodes adjacent to vocal folds and adhesive pre-gelled electrodes on the TC were used for EMG recording during IONM. Electrically evoked EMG signals detected by both electrode types were recorded and analyzed. EMG changes during tracheal displacement and RLN traction injury were compared. RESULTS: Both the ETT and TC recording electrodes recorded typical laryngeal EMG waveforms evoked by a 1 mA stimulus current applied on both sides of the RLNs and vagus nerves (VNs). Under RLN stimulation, the mean EMG amplitudes recorded with the ETT and TC electrodes were 973 ± 79 µV and 695 ± 150 µV, respectively. Under VN stimulation, the mean amplitudes were 841 ± 163 µV and 607 ± 162 µV, respectively. When upward displacement of the trachea was experimentally induced, the TC electrodes showed less variation in recorded EMG signals compared to ETT electrodes. When RLN traction stress was experimentally induced, both the ETT and TC electrodes accurately recorded the typical EMG pattern of progressively degrading amplitude and gradual recovery after release of traction. CONCLUSIONS: This study confirms the feasibility of using transcartilage surface electrodes for recording laryngeal EMG signals evoked during IONM in an animal model. However, before practical application of this approach in clinical thyroid surgery, further studies are needed to improve electrode designs by optimizing their shapes and sizes, and increasing their adhesive stability and sensitivity.

Technical development of transcutaneous electrical nerve inhibition using medium-frequency alternating current.

BACKGROUND: Innovative technical approaches to controlling undesired sensory and motor activity, such as hyperalgesia or spasticity, may contribute to rehabilitation techniques for improving neural plasticity in patients with neurologic disorders. To date, transcutaneous electrical stimulation has used low frequency pulsed currents for sensory inhibition and muscle activation. Yet, few studies have attempted to achieve motor nerve inhibition using transcutaneous electrical stimulation. This study aimed to develop a technique for transcutaneous electrical nerve inhibition (TENI) using medium-frequency alternating current (MFAC) to suppress both sensory and motor nerve activity in humans. METHODS: Surface electrodes were affixed to the skin of eight young adults to stimulate the median nerve. Stimulation intensity was increased up to 50% and 100% of the pain threshold. To identify changes in sensory perception by transcutaneous MFAC (tMFAC) stimulation, we examined tactile and pressure pain thresholds in the index and middle fingers before and after stimulation at 10 kHz. To demonstrate the effect of tMFAC stimulation on motor inhibition, stimulation was applied while participants produced flexion forces with the index and middle fingers at target forces (50% and 90% of MVC, maximum voluntary contraction). RESULTS: tMFAC stimulation intensity significantly increased tactile and pressure pain thresholds, indicating decreased sensory perception. During the force production task, tMFAC stimulation with the maximum intensity immediately reduced finger forces by ~ 40%. Finger forces recovered immediately after stimulation cessation. The effect on motor inhibition was greater with the higher target force (90% MVC) than with the lower target (50% MVC). Also, higher tMFAC stimulation intensity provided a greater inhibition effect on both sensory and motor nerve activity. CONCLUSION: We found that tMFAC stimulation immediately inhibits sensory and motor activity. This pre-clinical study demonstrates a novel technique for TENI using MFAC stimulation and showed that it can effectively inhibit both sensory perception and motor activity. The proposed technique can be combined with existing rehabilitation devices (e.g., a robotic exoskeleton) to inhibit undesired sensorimotor activities and to accelerate recovery after neurologic injury.

Transcutaneous Recording During Intraoperative Neuromonitoring in Thyroid Surgery.

BACKGROUND: Recurrent laryngeal nerve (RLN) palsy remains a major source of morbidity after thyroid surgeries. Intraoperative neural monitoring (IONM) has gained increasing acceptance as an adjunct to standard practice of visual RLN identification. Endotracheal tube (ETT) surface recording electrodes systems are now widely used for IONM; however, a malpositioned ETT can cause false IONM results and requires time-consuming intraoperative verification of the ETT position and readjustment by the anesthesiologist. The aim of this experimental study was to evaluate the feasibility of the transcutaneous approach for recording evoked laryngeal electromyography (EMG) signals during IONM. METHODS: A porcine model with well-established applicability in IONM research was used. Twelve piglets (24 nerve sides) were enrolled. Electrically evoked EMGs were recorded from surface electrodes on the ETT and from the adhesive pre-gelled surface electrodes on the anterior neck skin. The evoked EMG waveforms were measured and analyzed. The real-time signal stability of the electrodes during tracheal displacement and their accuracy in reflecting adverse EMG changes during RLN stress were evaluated during continuous IONM performed with automatic periodic vagus nerve (VN) stimulation. RESULTS: In all nerves, both the ETT and neck adhesive skin electrodes successfully recorded typical evoked laryngeal EMG waveforms from the RLNs and VNs under stimulation with 1 mA. The transcutaneous electrodes recorded mean EMG amplitudes of 264 µV (±79) under RLN stimulation and 202 µV (±55) under VN stimulation. The electrodes recorded mean EMG latencies of 2.98 ms (±0.20) under RLN stimulation, 4.51 ms (±0.50) under right VN stimulation, and 8.13 ms (±0.94) under left VN stimulation, respectively. When tracheal displacement was experimentally induced, the EMG signals obtained by ETT electrodes varied significantly, but those obtained by transcutaneous electrodes did not. When RLN traction stress was experimentally induced, both ETT and transcutaneous electrodes recorded the same pattern of progressively degrading EMG amplitude with gradual recovery after release of traction. CONCLUSIONS: This study confirms the feasibility of transcutaneous recording of evoked laryngeal EMG during IONM. Although this study confirms the stability and accuracy of the transcutaneous approach, it also revealed the need for new electrode designs to improve EMG amplitudes before practical clinical application of this approach.

Comparing DTL microfiber and Neuroline skin electrode in the Mini Ganzfeld ERG.

BACKGROUND: In infant ERG recordings skin electrodes frequently result in a better compliance. In order to assess the quality of such recordings, we compared the recording characteristics of DTL microfiber and Neuroline surface electrodes using a modified ISCEV protocol in the Mini Ganzfeld ERG. METHODS: A prospective cohort study on healthy adult subjects was conducted at the Department of Ophthalmology, University of Basel, Switzerland. Thirty healthy volunteers were tested. The microfiber electrode (DTL Plus Electrode) was placed across the cornea, above the lower eyelid. The Neuroline skin electrode was placed on the surface of the lower lid on the opposite eye. The eye on which each electrode type was placed was randomised. Amplitudes of the rod, standard combined, standard flash cone, light-adapted 3.0 Hz flicker and red cone responses were analysed, as well as their respective implicit times. RESULTS: Both electrode recordings showed the same waveform characteristics. Responses with the Neuroline electrode were significantly weaker than those from the DTL electrode. Amplitudes of the rod, standard combined, standard flash cone, light-adapted 3.0 Hz flicker and red cone responses were up to four times larger when recorded with the DTL electrode (p < 0.005, ANOVA). Implicit times of the red cone ERGs were slightly faster for the Neuroline skin electrode recordings (p ≤ 0.039). CONCLUSIONS: Comparison of full-field ERG recordings with microfiber DTL and Neuroline skin electrodes showed that DTL electrodes produce larger ERGs. Hence, we provide evidence that both electrode types allow successful full-field ERG recording, although separate normative data for both electrodes are necessary.

EMG classification using wavelet functions to determine muscle contraction.

Surface electromyogram (SEMG) is a complex signal and is influenced by several external factors/artifacts. The electromyogram signal from the stump of the subject is picked up through surface electrodes. It is amplified and artifacts are removed before digitising it in a controlled manner so that minimum signal loss occurs due to processing. As removing these artifacts is not easy, feature extraction to obtain useful information hidden inside the signal becomes a different process. This paper presents methods of analysing SEMG signals using discrete wavelet Transform (DWT) for extracting accurate patterns of the signals and the performance of the used algorithms is being analysed rigorously. The obtained results suggest a root mean square difference (RMSD) value for the denoising and quality of reconstruction of the SEMG signal. The result shows that the best mother wavelets for tolerance of noise are second order of symmlets and bior6.8. Results inferred that bior6.8 suitable for the classification and analysis of SEMG signals of different arm motions results in a classification accuracy of 88.90%.

Recording and assessment of evoked potentials with electrode arrays.

In order to optimize procedure for the assessment of evoked potentials and to provide visualization of the flow of action potentials along the motor systems, we introduced array electrodes for stimulation and recording and developed software for the analysis of the recordings. The system uses a stimulator connected to an electrode array for the generation of evoked potentials, an electrode array connected to the amplifier, A/D converter and computer for the recording of evoked potentials, and a dedicated software application. The method has been tested for the assessment of the H-reflex on the triceps surae muscle in six healthy humans. The electrode array with 16 pads was positioned over the posterior aspect of the thigh, while the recording electrode array with 16 pads was positioned over the triceps surae muscle. The stimulator activated all the pads of the stimulation electrode array asynchronously, while the signals were recorded continuously at all the recording sites. The results are topography maps (spatial distribution of evoked potentials) and matrices (spatial visualization of nerve excitability). The software allows the automatic selection of the lowest stimulation intensity to achieve maximal H-reflex amplitude and selection of the recording/stimulation pads according to predefined criteria. The analysis of results shows that the method provides rich information compared with the conventional recording of the H-reflex with regard the spatial distribution.