Validating the Comparison Framework for the Finite Dimensions Model of Concentric Ring Electrodes Using Human Electrocardiogram Data

[EN] While progress has been made in design optimization of concentric ring electrodes maximizing the accuracy of the surface Laplacian estimation, it was based exclusively on the negligible dimensions model of the electrode. Recent proof of concept of the new finite dimensions model that adds the radius of the central disc and the widths of concentric rings to the previously included number of rings and inter-ring distances provides an opportunity for more comprehensive design optimization. In this study, the aforementioned proof of concept was developed into a framework allowing direct comparison of any two concentric ring electrodes of the same size and with the same number of rings. The proposed framework is illustrated on constant and linearly increasing inter-ring distances tripolar concentric ring electrode configurations and validated on electrocardiograms from 20 human volunteers. In particular, ratios of truncation term coefficients between the two electrode configurations were used to demonstrate the similarity between the negligible and the finite dimension models analytically (p = 0.077). Laplacian estimates based on the two models were calculated on electrocardiogram data for emulation of linearly increasing inter-ring distances tripolar concentric ring electrode. The difference between the estimates was not statistically significant (p >> 0.05) which is consistent with the analytic result.This research was funded by the National Science Foundation (NSF) Division of Human Resource Development (HRD) Tribal Colleges and Universities Program (TCUP), grants number 1622481 and 1914787 to Oleksandr Makeyev. The authors would like to thank Rafael Rodriguez de Sanabria for his help with the human ECG data collection and Eduardo Garcia-Breijo for his help with the CRE implementation.Makeyev, O.; Musngi, M.; Moore, L.; Ye Lin, Y.; Prats-Boluda, G.; Garcia-Casado, J. (2019). Validating the Comparison Framework for the Finite Dimensions Model of Concentric Ring Electrodes Using Human Electrocardiogram Data. Applied Sciences. 9(20):1-14. https://doi.org/10.3390/app9204279S114920Bradshaw, L. A., Richards, W. O., & Wikswo, J. P. (2001). Volume conductor effects on the spatial resolution of magnetic fields and electric potentials from gastrointestinal electrical activity. Medical and Biological Engineering and Computing, 39(1), 35-43. doi:10.1007/bf02345264Besio, W. G., Hongbao Cao, & Peng Zhou. (2008). Application of Tripolar Concentric Electrodes and Prefeature Selection Algorithm for Brain–Computer Interface. IEEE Transactions on Neural Systems and Rehabilitation Engineering, 16(2), 191-194. doi:10.1109/tnsre.2007.916303Farina, D., & Cescon, C. (2001). Concentric-ring electrode systems for noninvasive detection of single motor unit activity. IEEE Transactions on Biomedical Engineering, 48(11), 1326-1334. doi:10.1109/10.959328McFarland, D. 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Textile Concentric Ring Electrodes for ECG Recording Based on Screen-Printing Technology. Sensors, 18(1), 300. doi:10.3390/s18010300Besio, W. G., Martinez-Juarez, I. E., Makeyev, O., Gaitanis, J. N., Blum, A. S., Fisher, R. S., & Medvedev, A. V. (2014). High-Frequency Oscillations Recorded on the Scalp of Patients With Epilepsy Using Tripolar Concentric Ring Electrodes. IEEE Journal of Translational Engineering in Health and Medicine, 2, 1-11. doi:10.1109/jtehm.2014.2332994Boudria, Y., Feltane, A., & Besio, W. (2014). Significant improvement in one-dimensional cursor control using Laplacian electroencephalography over electroencephalography. Journal of Neural Engineering, 11(3), 035014. doi:10.1088/1741-2560/11/3/035014Garcia-Casado, J., Zena-Gimenez, V., Prats-Boluda, G., & Ye-Lin, Y. (2013). Enhancement of Non-Invasive Recording of Electroenterogram by Means of a Flexible Array of Concentric Ring Electrodes. 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Functional characterisation of a complex mutation in the α(1,4)galactosyltransferase gene in Taiwanese individuals with p phenotype. Transfusion Medicine, 21(2), 84-89. doi:10.1111/j.1365-3148.2010.01055.xMakeyev, O., Ding, Q., & Besio, W. G. (2016). Improving the accuracy of Laplacian estimation with novel multipolar concentric ring electrodes. Measurement, 80, 44-52. doi:10.1016/j.measurement.2015.11.017Makeyev, O., & Besio, W. (2016). Improving the Accuracy of Laplacian Estimation with Novel Variable Inter-Ring Distances Concentric Ring Electrodes. Sensors, 16(6), 858. doi:10.3390/s16060858Makeyev, O. (2018). Solving the general inter-ring distances optimization problem for concentric ring electrodes to improve Laplacian estimation. BioMedical Engineering OnLine, 17(1). doi:10.1186/s12938-018-0549-6Ye-Lin, Y., Bueno-Barrachina, J. M., Prats-boluda, G., Rodriguez de Sanabria, R., & Garcia-Casado, J. (2017). 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Ambulatory External Electrocardiographic Monitoring. Journal of the American College of Cardiology, 58(17), 1741-1749. doi:10.1016/j.jacc.2011.07.026Garcia-Casado, J., Ye-Lin, Y., Prats-Boluda, G., & Makeyev, O. (2019). Evaluation of Bipolar, Tripolar, and Quadripolar Laplacian Estimates of Electrocardiogram via Concentric Ring Electrodes. Sensors, 19(17), 3780. doi:10.3390/s19173780Xu, Y., Luo, M., Li, T., & Song, G. (2017). ECG Signal De-noising and Baseline Wander Correction Based on CEEMDAN and Wavelet Threshold. Sensors, 17(12), 2754. doi:10.3390/s17122754Ortigueira, M. D., Laleg-Kirati, T.-M., & Machado, J. A. T. (2014). Riesz potential versus fractional Laplacian. Journal of Statistical Mechanics: Theory and Experiment, 2014(9), P09032. doi:10.1088/1742-5468/2014/09/p0903

Textile Concentric Ring Electrodes for ECG Recording Based on Screen-Printing Technology

[EN] Among many of the electrode designs used in electrocardiography (ECG), concentric ring electrodes (CREs) are one of the most promising due to their enhanced spatial resolution. Their development has undergone a great push due to their use in recent years; however, they are not yet widely used in clinical practice. CRE implementation in textiles will lead to a low cost, flexible, comfortable, and robust electrode capable of detecting high spatial resolution ECG signals. A textile CRE set has been designed and developed using screen-printing technology. This is a mature technology in the textile industry and, therefore, does not require heavy investments. Inks employed as conductive elements have been silver and a conducting polymer (poly (3,4-ethylenedioxythiophene) polystyrene sulfonate; PEDOT: PSS). Conducting polymers have biocompatibility advantages, they can be used with flexible substrates, and they are available for several printing technologies. CREs implemented with both inks have been compared by analyzing their electric features and their performance in detecting ECG signals. The results reveal that silver CREs present a higher average thickness and slightly lower skin-electrode impedance than PEDOT: PSS CREs. As for ECG recordings with subjects at rest, both CREs allowed the uptake of bipolar concentric ECG signals (BC-ECG) with signal-to-noise ratios similar to that of conventional ECG recordings. Regarding the saturation and alterations of ECGs captured with textile CREs caused by intentional subject movements, silver CREs presented a more stable response (fewer saturations and alterations) than those of PEDOT: PSS. Moreover, BC-ECG signals provided higher spatial resolution compared to conventional ECG. This improved spatial resolution was manifested in the identification of P1 and P2 waves of atrial activity in most of the BC-ECG signals. It can be concluded that textile silver CREs are more suitable than those of PEDOT: PSS for obtaining BC-ECG records. These developed textile electrodes bring the use of CREs closer to the clinical environment.Grant from the Ministerio de Economia y Competitividad y del Fondo Europeo de Desarrollo Regional. DPI2015-68397-R (MINECO/FEDER). This work was also supported by the Spanish Government/FEDER funds (grant number MAT2015-64139-C4-3-R (MINECO/FEDER)).Lidon-Roger, JV.; Prats-Boluda, G.; Ye Lin, Y.; Garcia Casado, FJ.; Garcia-Breijo, E. (2018). Textile Concentric Ring Electrodes for ECG Recording Based on Screen-Printing Technology. Sensors. 18(1):300-314. https://doi.org/10.3390/s18010300S30031418

Doctor of Philosophy

dissertationAtrial fibrillation (AF) is the leading cause of ischemic stroke and is the most commonly observed arrhythmia in clinical cardiology. Catheter ablation of AF, in which specific regions of cardiac anatomy associated with AF are intenionally injured to create scar tissue, has been honed over the last 15 years to become a relatively common and safe treatment option. However, the success of these anatomically driven ablation strategies, particularly in hearts that have been exposed to AF for extended periods, remains poor. AF induces changes in the electrical and structural properties of the cardiac tissue that further promotes the permanence of AF. In a process known as electroanatomical (EAM) mapping, clinicians record time signals known as electrograms (EGMs) from the heart and the locations of the recording sites to create geometric representations, or maps, of the electrophysiological properties of the heart. Analysis of the maps and the individual EGM morphologies can indicate regions of abnormal tissue, or substrates that facilitate arrhythmogenesis and AF perpetuation. Despite this progress, limitations in the control of devices currently used for EAM acquisition and reliance on suboptimal metrics of tissue viability appear to be hindering the potential of treatment guided by substrate mapping. In this research, we used computational models of cardiac excitation to evaluate param- eters of EAM that affect the performance of substrate mapping. These models, which have been validated with experimental and clinical studies, have yielded new insights into the limitations of current mapping systems, but more importantly, they guided us to develop new systems and metrics for robust substrate mapping. We report here on the progress in these simulation studies and on novel measurement approaches that have the potential to improve the robustness and precision of EAM in patients with arrhythmias. Appropriate detection of proarrhythmic substrates promises to improve ablation of AF beyond rudimentary destruction of anatomical targets to directed targeting of complicit tissues. Targeted treatment of AF sustaining tissues, based on the substrate mapping approaches described in this dissertation, has the potential to improve upon the efficacy of current AF treatment options

Non-invasive identification of atrial fibrillation drivers

Atrial fibrillation (AF) is one of the most common cardiac arrhythmias. Nowadays the fibrillatory process is known to be provoked by the high-frequency reentrant activity of certain atrial regions that propagates the fibrillatory activity to the rest of the atrial tissue, and the electrical isolation of these key regions has demonstrated its effectiveness in terminating the fibrillatory process. The location of the dominant regions represents a major challenge in the diagnosis and treatment of this arrhythmia. With the aim to detect and locate the fibrillatory sources prior to surgical procedure, non-invasive methods have been developed such as body surface electrical mapping (BSPM) which allows to record with high spatial resolution the electrical activity on the torso surface or the electrocardiographic imaging (ECGI) which allows to non-invasively reconstruct the electrical activity in the atrial surface. Given the novelty of these systems, both technologies suffer from a lack of scientific knowledge about the physical and technical mechanisms that support their operation. Therefore, the aim of this thesis is to increase that knowledge, as well as studying the effectiveness of these technologies for the localization of dominant regions in patients with AF. First, it has been shown that BSPM systems are able to noninvasively identify atrial rotors by recognizing surface rotors after band-pass filtering. Furthermore, the position of such surface rotors is related to the atrial rotor location, allowing the distinction between left or right atrial rotors. Moreover, it has been found that the surface electrical maps in AF suffer a spatial smoothing effect by the torso conductor volume, so the surface electrical activity can be studied with a relatively small number of electrodes. Specifically, it has been seen that 12 uniformly distributed electrodes are sufficient for the correct identification of atrial dominant frequencies, while at least 32 leads are needed for non-invasive identification of atrial rotors. Secondly, the effect of narrowband filtering on the effectiveness of the location of reentrant patterns was studied. It has been found that this procedure allows isolating the reentrant electrical activity caused by the rotor, increasing the detection rate for both invasive and surface maps. However, the spatial smoothing caused by the regularization of the ECGI added to the temporal filtering causes a large increase in the spurious reentrant activity, making it difficult to detect real reentrant patterns. However, it has been found that maps provided by the ECGI without temporal filtering allow the correct detection of reentrant activity, so narrowband filtering should be applied for intracavitary or surface signal only. Finally, we studied the stability of the markers used to detect dominant regions in ECGI, such as frequency maps or the rotor presence. It has been found that in the presence of alterations in the conditions of the inverse problem, such as electrical or geometrical noise, these markers are significantly more stable than the ECGI signal morphology from which they are extracted. In addition, a new methodology for error reduction in the atrial spatial location based on the curvature of the curve L has been proposed. The results presented in this thesis showed that BSPM and ECGI systems allows to non-invasively locate the presence of high-frequency rotors, responsible for the maintenance of AF. This detection has been proven to be unambiguous and robust, and the physical and technical mechanisms that support this behavior have been studied. These results indicate that both non-invasive systems provide information of great clinical value in the treatment of AF, so their use can be helpful for selecting and planning atrial ablation procedures.La fibrilación auricular (FA) es una de las arritmias cardiacas más frecuentes. Hoy en día se sabe que el proceso fibrilatorio está provocado por la actividad reentrante a alta frecuencia de ciertas regiones auriculares que propagan la actividad fibrilatoria en el resto del tejido auricular, y se ha demostrado que el aislamiento eléctrico de estas regiones dominantes permite detener el proceso fibrilatorio. La localización de las regiones dominantes supone un gran reto en el diagnóstico y tratamiento de la FA. Con el objetivo de poder localizar las fuentes fibrilatorias con anterioridad al procedimiento quirúrgico, se han desarrollado métodos no invasivos como la cartografía eléctrica de superficie (CES) que registra con gran resolución espacial la actividad eléctrica en la superficie del torso o la electrocardiografía por imagen (ECGI) que permite reconstruir la actividad eléctrica en la superficie auricular. Dada la novedad de estos sistemas, existe una falta de conocimiento científico sobre los mecanismos físicos y técnicos que sustentan su funcionamiento. Por lo tanto, el objetivo de esta tesis es aumentar dicho conocimiento, así como estudiar la eficacia de ambas tecnologías para la localización de regiones dominantes en pacientes con FA. En primer lugar, ha visto que los sistemas CES permiten identificar rotores auriculares mediante el reconocimiento de rotores superficiales tras el filtrado en banda estrecha. Además, la posición de los rotores superficiales está relacionada con la localización de dichos rotores, permitiendo la distinción entre rotores de aurícula derecha o izquierda. Por otra parte, se ha visto que los mapas eléctricos superficiales durante FA sufren una gran suavizado espacial por el efecto del volumen conductor del torso, lo que permite que la actividad eléctrica superficial pueda ser estudiada con un número relativamente reducido de electrodos. Concretamente, se ha visto que 12 electrodos uniformemente distribuidos son suficientes para una correcta identificación de frecuencias dominantes, mientras que son necesarios al menos 32 para una correcta identificación de rotores auriculares. Por otra parte, también se ha estudiado el efecto del filtrado en banda estrecha sobre la eficacia de la localización de patrones reentrantes. Así, se ha visto que este procedimiento permite aislar la actividad eléctrica reentrante provocada por el rotor, aumentando la tasa de detección tanto para señal obtenida de manera invasiva como para los mapas superficiales. No obstante, este filtrado temporal sobre la señal de ECGI provoca un gran aumento de la actividad reentrante espúrea que dificulta la detección de patrones reentrantes reales. Sin embargo, los mapas ECGI sin filtrado temporal permiten la detección correcta de la actividad reentrante, por lo el filtrado debería ser aplicado únicamente para señal intracavitaria o superficial. Por último, se ha estudiado la estabilidad de los marcadores utilizados en ECGI para detectar regiones dominantes, como son los mapas de frecuencia o la presencia de rotores. Se ha visto que en presencia de alteraciones en las condiciones del problema inverso, como ruido eléctrico o geométrico, estos marcadores son significativamente más estables que la morfología de la propia señal ECGI. Además, se ha propuesto una nueva metodología para la reducción del error en la localización espacial de la aurícula basado en la curvatura de la curva L. Los resultados presentados en esta tesis revelan que los sistemas de CES y ECGI permiten localizar de manera no invasiva la presencia de rotores de alta frecuencia. Esta detección es univoca y robusta, y se han estudiado los mecanismos físicos y técnicos que sustentan dicho comportamiento. Estos resultados indican que ambos sistemas no invasivos proporcionan información de gran valor clínico en el tratamiento de la FA, por lo que su uso puede ser de gran ayuda para la selección y planificaciLa fibril·lació auricular (FA) és una de les arítmies cardíaques més freqüents. Hui en dia es sabut que el procés fibrilatori està provocat per l'activitat reentrant de certes regions auriculars que propaguen l'activitat fibril·latoria a la resta del teixit auricular, i s'ha demostrat que l'aïllament elèctric d'aquestes regions dominants permet aturar el procés fibrilatori. La localització de les regions dominants suposa un gran repte en el diagnòstic i tractament d'aquesta arítmia. Amb l'objectiu de poder localitzar fonts fibril·latories amb anterioritat al procediment quirúrgic s'han desenvolupat mètodes no invasius com la cartografia elèctrica de superfície (CES) que registra amb gran resolució espacial l'activitat elèctrica en la superfície del tors o l'electrocardiografia per imatge (ECGI) que permet obtenir de manera no invasiva l'activitat elèctrica en la superfície auricular. Donada la relativa novetat d'aquests sistemes, existeix una manca de coneixement científic sobre els mecanismes físics i tècnics que sustenten el seu funcionament. Per tant, l'objectiu d'aquesta tesi és augmentar aquest coneixement, així com estudiar l'eficàcia d'aquestes tecnologies per a la localització de regions dominants en pacients amb FA. En primer lloc, s'ha vist que els sistemes CES permeten identificar rotors auriculars mitjançant el reconeixement de rotors superficials després del filtrat en banda estreta. A més, la posició dels rotors superficials està relacionada amb la localització d'aquests rotors, permetent la distinció entre rotors de aurícula dreta o esquerra. També s'ha vist que els mapes elèctrics superficials durant FA pateixen un gran suavitzat espacial per l'efecte del volum conductor del tors, el que permet que l'activitat elèctrica superficial pugui ser estudiada amb un nombre relativament reduït d'elèctrodes. Concretament, s'ha vist que 12 elèctrodes uniformement distribuïts són suficients per a una correcta identificació de freqüències dominants auriculars, mentre que són necessaris almenys 32 per a una correcta identificació de rotors auriculars. D'altra banda, també s'ha estudiat l'efecte del filtrat en banda estreta sobre l'eficàcia de la localització de patrons reentrants. Així, s'ha vist que aquest procediment permet aïllar l'activitat elèctrica reentrant provocada pel rotor, augmentant la taxa de detecció tant pel senyal obtingut de manera invasiva com per als mapes superficials. No obstant això, aquest filtrat temporal sobre el senyal de ECGI provoca un gran augment de l'activitat reentrant espúria que dificulta la detecció de patrons reentrants reals. A més, els mapes proporcionats per la ECGI sense filtrat temporal permeten la detecció correcta de l'activitat reentrant, per la qual cosa el filtrat hauria de ser aplicat únicament per a senyal intracavitària o superficial. Per últim, s'ha estudiat l'estabilitat dels marcadors utilitzats en ECGI per a detectar regions auriculars dominants, com són els mapes de freqüència o la presència de rotors. S'ha vist que en presència d'alteracions en les condicions del problema invers, com soroll elèctric o geomètric, aquests marcadors són significativament més estables que la morfologia del mateix senyal ECGI. A més, s'ha proposat una nova metodologia per a la reducció de l'error en la localització espacial de l'aurícula basat en la curvatura de la corba L. Els resultats presentats en aquesta tesi revelen que els sistemes de CES i ECGI permeten localitzar de manera no invasiva la presència de rotors d'alta freqüència. Aquesta detecció és unívoca i robusta, i s'han estudiat els mecanismes físics i tècnics que sustenten aquest comportament. Aquests resultats indiquen que els dos sistemes no invasius proporcionen informació de gran valor clínic en el tractament de la FA, pel que el seu ús pot ser de gran ajuda per a la selecció i planificació de procediments d'ablació auricular.Rodrigo Bort, M. (2016). Non-invasive identification of atrial fibrillation drivers [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/75346TESISPremios Extraordinarios de tesis doctorale

Evaluación no invasiva del impulso neural respiratorio y su relación con la respuesta mecánica mediante el análisis de señales electromiográficas de músculos respiratorios

Respiratory muscle contraction occurs in response to the electrical stimulation of the muscles. These electrical stimuli originate in the respiratory neurons of the brainstem, are transmitted via motor nerves to the neuromuscular junctions and propagate along muscle fibers. Respiratory electromyography measures the electrical activity of respiratory muscles in response to this nerve stimulation. The neural respiratory drive (NRD) is best expressed in a phrenic neurogram, but this is not feasible in humans. Alternatively, measurements of the diaphragm electromyographic signal (EMGdi) would most likely reflect phrenic neurogram activity. EMGdi signal can be recorded using invasive methods, involving the use of needle electrodes or electrodes positioned in the esophagus at the level of the diaphragm. As a non-invasive alternative, the study of respiratory muscle activity can be addressed by surface electromyography. The onset and offset of the neural inspiratory time (nton and ntoff, respectively) are fundamentally important measurements in studies of patient-ventilator interaction, where the level of assistance delivered by the ventilator is controlled by patient demand. Cardiac artifacts (ECG) often make it difficult to utilize EMGdi. To overcome the shortcoming of the ECG, in this thesis is proposed to use sample entropy with fixed tolerance values (fSampEn), a robust technique against impulsive noise. To evaluate nton and ntoff estimation it has been carried out an experimental study with surface EMGdi signals recorded in healthy subjects during two respiratory protocols designed to evaluate the influence of different breathing patterns on the EMGdi. These protocols consisted of a stepwise increase in respiratory rate (RR) with constant fractional inspiratory time (Ti/Ttot) and a stepwise decrement in the Ti/Ttot with constant RR, respectively. The developed algorithms allowed to determine the nton and ntoff and derive the RR, Ti and Ti/Ttot neural ventilatory parameters. The EMGdi amplitude provides a real-time indirect measure of the NRD, which reflects the load on the respiratory muscles. The NRD, assessed by normalized EMGdi signals, is higher in patients with respiratory disease than in healthy subjects. To evaluate the behavior of the fSamp En, as a method for improving the measurement of NRD from EMGdi signals in the presence of cardiac activity, compared to the average rectified value and root mean square value approaches, first, these methods have been applied to synthetic EMGdi signals . Secondly, we tested the proposed methods in an experimental study with EMGdi signals recorded in healthy subjects during an incremental inspiratory load test. The EMGdi amplitude allowed to evaluate changes in the respiratory muscle activation patterns and estimate the NRD. Also, this thesis contributes to the study of the respiratory activity by the non-invasive recording of mechanomyographic low frequency (BF) activity in healthy subjects and in patients with chronic obstructive pulmonary disease, allowing the study of bilateral asynchrony of the diaphragm and the RR. Finally, we have proposed the use of concentric ring electrodes as an alternative to improve the spatial resolution of electromyographic recordings, and eliminate the problems associated with the location and orientation of the bipolar configuration. The approaches presented in this doctoral thesis based on the analysis of electromyographic and mechanomyographic signals of respiratory museles allow to extract complementary information to current use techniques of and contribute to the study of respiratory function in the clinical setting .La contracción de los músculos respiratorios se produce en respuesta a la estimulación eléctrica. Estos estímulos se originan en las neuronas respiratorias del tronco del encéfalo, se transmiten a través de los nervios motores a las uniones neuromusculares y se propagan a lo largo de las fibras musculares. La electromiografía respiratoria mide la actividad eléctrica de los músculos respiratorios en respuesta a esta estimulación nerviosa. El impulso neural respiratorio (NRD) se expresa mejor a través del neurograma frénico, pero esto no es factible en los seres humanos. Como alternativa, la medida de la señal electromiográfica del diafragma (EMGdi) refleja de forma indirecta la actividad frénica. La señal EMGdi puede registrarse utilizando métodos invasivos, lo que implica el uso de electrodos de aguja o electrodos colocados en el esófago a nivel del diafragma . Como alternativa no invasiva, el estudio de la actividad muscular respiratoria puede abordarse mediante la electromiografía de superficie. El inicio y fin del tiempo neural inspiratorio (nton y ntoff, respectivamente) son medidas de importancia en los estudios de interacción paciente-ventilador, donde el nivel de la asistencia proporcionada por el ventilador es controlado por la demanda del paciente. Los artefactos cardíacos (ECG) a menudo hacen que sea difícil de utilizar la señal EMGdi. Para superar el inconveniente de la interferencia ECG, en la presente tesis se propone utilizar la entropía muestra! con valores de tolerancia fijos (fSampEn), una técnica que es robusta contra el ruido de tipo impulsivo. Para evaluar la estimación del nton y ntoff se ha realizado un estudio experimental con señales EMGdi superficie registrada en sujetos sanos durante dos protocolos respiratorios, diseñados para evaluar la influencia de los diferentes patrones respiratorios sobre la señal EMGdi. Estos protocolos consistieron en un aumento gradual de la frecuencia respiratoria (RR) con un tiempo inspiratorio (Ti) fracciona! constante (Ti!Ttot) y en una disminución gradual en el Ti!Ttot con una RR constante, respectivamente. Los algoritmos desarrollados han permitido determinar el nton y el ntoff y derivar los parámetros ventilatorios RR, Ti, y TifTtot neurales. La amplitud de la EMGdi proporciona una medida indirecta del NRD, que refleja la carga sobre los músculos respiratorios. El NRD, evaluado en señales EMGdi normalizadas, es mayor en pacientes con enfermedades respiratorias que en sujetos sanos. Para evaluar el comportamiento de la fSampEn, como un método para mejorar la medición del NRD a partir de señales EMGdi en presencia de ECG, en comparación con los enfoques basados en el uso del valor rectificado medio y valor cuadrático medio, primero, se han aplicado estos métodos a señales EMGdi sintéticas . En segundo lugar, hemos probado los métodos propuestos en un estudio experimental con señales EMGdi registradas en sujetos sanos durante una prueba de carga inspiratoria incremental. La amplitud de la EMGdi permitió evaluar los cambios en el patrón de activación de los músculos respiratorios y estimar el NRO. Asimismo, esta tesis doctoral contribuye al estudio de la actividad respiratoria mediante el registro no invasivo de actividad mecanomiográfica de baja frecuencia (BF) en sujetos sanos y en pacientes con enfermedad obstructiva crónica, permitiendo el estudio de la asincronía bilateral del diafragma y la RR. Finalmente, hemos propuesto el uso de electrodos de anillos concéntricos como una alternativa para mejorar la resolución espacial de los registros electromiográficos, y eliminar los problemas asociados a la localización y orientación de la configuración bipolar. Los enfoques presentados en esta tesis doctoral basados en el análisis de señales electromiográficas y mecanomiográficas de los músculo

Computational Intelligence in Electromyography Analysis

Electromyography (EMG) is a technique for evaluating and recording the electrical activity produced by skeletal muscles. EMG may be used clinically for the diagnosis of neuromuscular problems and for assessing biomechanical and motor control deficits and other functional disorders. Furthermore, it can be used as a control signal for interfacing with orthotic and/or prosthetic devices or other rehabilitation assists. This book presents an updated overview of signal processing applications and recent developments in EMG from a number of diverse aspects and various applications in clinical and experimental research. It will provide readers with a detailed introduction to EMG signal processing techniques and applications, while presenting several new results and explanation of existing algorithms. This book is organized into 18 chapters, covering the current theoretical and practical approaches of EMG research

Design of a wearable device for conditional neuromodulation of the pudendal nerve

After spinal cord injury, the normal functions of the lower urinary tract may be disrupted. Namely, incontinence and concurrent voiding problems may ensue. The troublesome side effects of the drugs, infection due to catheterisation, and the costs and risks associated with more invasive treatments indicate the need for alternative forms of treatment. The pudendal nerve neuromodulation may provide such an alternative. The unique aspect of this technique is that depending on the stimulus frequency it may result in micturition-like or continence-like reflexes. Also, the stimulus current can be applied trans-rectally, meaning that a minimally-invasive wearable solution may be developed. The major limitation of such a solution is the high level of the required stimulus current to activate the nerve trans-rectally. The efficacy of the trans-rectal neuromodulation of the pudendal may be increased by only applying the stimulus when needed, when employed to tackle incontinence. The electromyogram signal from the external anal sphincter may be used to detect the onset of hyper-reflexive contractions of the bladder. The ability of recording this signal can be readily incorporated in the neuromodulation device due to the proximity of the structures. However, the recording electrodes should be designed for an efficacious and chronic recording. Thus, the main objective of this thesis was to design and optimise the neuromodulation and recording electrodes on the said device. A volume conductor model of such a device in situ was developed and used in tandem with a double layer cable model of nerve fibres to minimise the stimulus current. It was demonstrated that a considerable reduction in the stimulus current may be achieved even when the variations of the nerve trajectory in different individuals are considered. Using computational models and experimental measurements, a recording assembly was identified for an efficacious recording of the electromyogram from the external anal sphincter

Improving the Accuracy of Laplacian Estimation with Novel Variable Inter-Ring Distances Concentric Ring Electrodes

Noninvasive concentric ring electrodes are a promising alternative to conventional disc electrodes. Currently, the superiority of tripolar concentric ring electrodes over disc electrodes, in particular, in accuracy of Laplacian estimation, has been demonstrated in a range of applications. In our recent work, we have shown that accuracy of Laplacian estimation can be improved with multipolar concentric ring electrodes using a general approach to estimation of the Laplacian for an (n + 1)-polar electrode with n rings using the (4n + 1)-point method for n ≥ 2. This paper takes the next step toward further improving the Laplacian estimate by proposing novel variable inter-ring distances concentric ring electrodes. Derived using a modified (4n + 1)-point method, linearly increasing and decreasing inter-ring distances tripolar (n = 2) and quadripolar (n = 3) electrode configurations are compared to their constant inter-ring distances counterparts. Finite element method modeling and analytic results are consistent and suggest that increasing inter-ring distances electrode configurations may decrease the truncation error resulting in more accurate Laplacian estimates compared to respective constant inter-ring distances configurations. For currently used tripolar electrode configuration, the truncation error may be decreased more than two-fold, while for the quadripolar configuration more than a six-fold decrease is expected

Electrophysiology

The outstanding evolution of recording techniques paved the way for better understanding of electrophysiological phenomena within the human organs, including the cardiovascular, ophthalmologic and neural systems. In the field of cardiac electrophysiology, the development of more and more sophisticated recording and mapping techniques made it possible to elucidate the mechanism of various cardiac arrhythmias. This has even led to the evolution of techniques to ablate and cure most complex cardiac arrhythmias. Nevertheless, there is still a long way ahead and this book can be considered a valuable addition to the current knowledge in subjects related to bioelectricity from plants to the human heart