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  • Evaluation of Laplacian diaphragm electromyographic recordings in a static inspiratory maneuver

     Estrada, Luis; Torres Cebrian, Abel; Garcia Casado, Javier; Ye-Lin, Y.; Jane Campos, Raimon
    Mediterranean Conference on Medical and Biological Engineering and Computing
    Presentation's date: 2014-09-27
    Presentation of work at congresses

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    Diaphragm electromyography (EMGdi) provides important information on diaphragm activity, to detect neuromuscular disorders of the most important muscle in the breathing inspiratory phase. EMGdi is habitually recorded using needles or esophageal catheters, with the implication of being invasive for patients. Surface electrodes offer an alternative for the non-invasive assessment of diaphragm activity. Ag/AgCl surface disc electrodes are used in monopolar or bipolar configuration to record EMGdi signals. On the other hand, Laplacian surface potential can be estimated by signal recording through active concentric ring electrodes. This kind of recording could reduce physiological interferences, increase the spatial selectivity and reduce orientation problems in the electrode location. The aim of this work is to compare EMGdi signals recorded simultaneously with disc electrodes in bipolar configuration and a Laplacian ring electrode over chest wall. EMGdi signal was recorded in one healthy subject during a breath hold maneuver and a static inspiratory maneuver based on Mueller¿s technique. In order to estimate the covered frequency range and the degree of noise contamination in both bipolar and Laplacian EMGdi signals, the cumulative percentage of the power spectrum and the signal to noise ratio in sub-bands were determined. Furthermore, diaphragm fatigue was evaluated by means of amplitude and frequency parameters. Our findings suggest that Laplacian EMGdi recording covers a broader frequency range although with higher noise contamination compared to bipolar EMGdi recording. Finally, in Laplacian recording fatigue indexes showed a clearer trend for muscle fatigue detection and also a reduced cardiac interference, providing an alternative to bipolar recording for diaphragm fatigue studies.

  • Features extraction method for brain-machine communication based on the empirical mode decomposition

     Diez, Pablo F.; Mut, Vicente A.; Laciar, Eric; Torres Cebrian, Abel; Avila Perona, Enrique M.
    Biomedical Engineering: Applications, Basis and Communications
    Date of publication: 2013-07
    Journal article

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    A brain-machine interface (BMI) is a communication system that translates human brain activity into commands, and then these commands are conveyed to a machine or a computer. It is proposes a technique for features extraction from electroencephalographic (EEG) signals and afterward, their classification on different mental tasks. The empirical mode decomposition (EMD) is a method capable of processing non-stationary and nonlinear signals, as the EEG. The EMD was applied on EEG signals of seven subjects performing five mental tasks. Six features were computed, namely, root mean square (RMS), variance, Shannon entropy, Lempel-Ziv complexity value, and central and maximum frequencies. In order to reduce the dimensionality of the feature vector, the Wilks' lambda (WL) parameter was used for the selection of the most important variables. The classification of mental tasks was performed using linear discriminant analysis (LDA) and neural networks (NN). Using this method, the average classification over all subjects in database is 91 5% and 87 5% using LDA and NN, respectively. Bit rate was ranging from 0.24 bits/trial up to 0.84 bits/trial. The proposed method allows achieving higher performances in the classification of mental tasks than other traditional methods using the same database. This represents an improvement in the brain-machine communication system. 2013 National Taiwan University.

  • Cardiac interference reduction in diaphragmatic MMG signals during a maintained inspiratory pressure test

     Sarlabous, Leonardo; Torres Cebrian, Abel; Fiz, José Antonio; Jane Campos, Raimon
    IEEE Engineering in Medicine and Biology Society
    Presentation's date: 2013-07
    Presentation of work at congresses

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    A recursive least square (RLS) adaptive filtering algorithm for reduction of cardiac interference in diaphragmatic mecanomyographic (MMGdi) signals is addressed in this paper. MMGdi signals were acquired with a capacitive accelerometer placed between 7th and 8th intercostal spaces, on the right anterior axillary line, during a maintained inspiratory pressure test. Subjects were asked to maintain a constant inspiratory pressure with a mouthpiece connected to a closed tube (without breathing). This maneuver was repeated at five different contraction efforts: apnea (no effort), 20 cmH2O, 40 cmH2O, 60 cmH2O and maximum voluntary contraction. An adaptive noise canceller (ANC) using the RLS algorithm was applied on the MMGdi signals. To evaluate the behavior of the ANC, the MMGdi signals were analyzed in two segments: with and without cardiac interference (WCI and NCI, respectively). In both segments it was analyzed the power spectral density (PSD), and the ARV and RMS amplitude parameters for each contraction effort. With the proposed ANC algorithm the amplitude parameters of the WCI segments were reduced to a level similar to the one of the NCI segments. The obtained results showed that ANC using the RLS algorithm allows to significantly reduce the cardiac interference in MMGdi signals.

  • Cancellation of cardiac interference in diaphragm EMG signals using an estimate of ECG reference signal

     Torres Cebrian, Abel; Fiz, José Antonio; Jane Campos, Raimon
    Mediterranean Conference on Medical and Biological Engineering and Computing
    Presentation's date: 2013-09-27
    Presentation of work at congresses

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    The analysis of the electromyographic signal of the diaphragm muscle (EMGdi) can provide important information in order to evaluate the respiratory muscular function. However, EMGdi signals are usually contaminated by the electrocardiographic (ECG) signal. An adaptive noise cancellation (ANC) based on event-synchronous cancellation can be used to reduce the ECG interference in the recorded EMGdi activity. In this paper, it is proposed an ANC scheme for cancelling the ECG interference in EMGdi signals using only the EMGdi signal (without acquiring the ECG signal). In this case the detection of the QRS complex has been performed directly in the EMGdi signal, and the ANC algorithm must be robust to false or missing QRS detections. Furthermore, an automatic criterion to select the adaptive constant of the LMS algorithm has been proposed (µ). The µ constant is selected automatically so that the canceling signal energy equals the energy of the reference signal (which is an estimation of the ECG interference present in the EMGdi signal). This approach optimizes the tradeoff between cancellation of ECG interference and attenuation of EMG component. A number of weights equivalent of a time window that contains several QRS complexes is selected in order to make the algorithm robust to QRS detection errors.

  • Characterization of laplacian surface electromyographic signals during isometric contraction in biceps brachii

     Estrada, Luis; Torres Cebrian, Abel; Garcia Casado, Javier; Prats Boluda, Gema; Jane Campos, Raimon
    IEEE Engineering in Medicine and Biology Society
    Presentation's date: 2013-07
    Presentation of work at congresses

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    Surface electromyography (sEMG) is a noninvasive technique for monitoring the electrical activity produced by the muscles. Usually, sEMG is performed by carrying out monopolar or bipolar recordings by means of conventional Ag/AgCl electrodes. In contrast, Laplacian recordings of sEMG could also be obtained by using coaxial ring electrodes. Laplacian recordings increase spatial resolution and attenuate other distant bioelectric interferences. Nevertheless, the spectral characteristics of this kind of recordings have been scarcely studied. The objective of this paper is to characterize the sEMG signals recorded with a Laplacian ring electrode and to compare them with traditional bipolar recordings with disc electrodes. Both kinds of signals were collected simultaneously in two healthy subjects during resting and sustained isometric voluntary contraction activities in biceps brachii. The conducted study computed the cumulative percentage of the power spectrum of sEMG so as to determine the energy bandwidth of the two kinds of recordings and the signal to noise ratio in different bands of the sEMG spectrum. Also, muscle fatigue, a condition when muscle force is reduced, was assessed using indexes from amplitude and frequency domain. The results of this study suggest that Laplacian sEMG has higher spectral bandwidth but a lower signal to noise ratio in comparison to bipolar sEMG. In addition, frequency fatigue indexes showed that Laplacian recording had better response than bipolar recording, which suggests that Laplacian electrode can be useful to study muscular fatigue due to better spatial resolution.

  • Index for estimation of muscle force from mechanomyogrpahy based on the Lempel-Ziv algorithm

     Sarlabous, Leonardo; Torres Cebrian, Abel; Fiz, José Antonio; Morera, Josep; Jane Campos, Raimon
    Journal of electromyography and kinesiology
    Date of publication: 2013-02-19
    Journal article

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    The study of the amplitude of respiratory muscle mechanomyographic (MMG) signals could be useful in clinical practice as an alternative non-invasive technique to assess respiratory muscle strength. The MMG signal is stochastic in nature, and its amplitude is usually estimated by means of the average rectified value (ARV) or the root mean square (RMS) of the signal. Both parameters can be used to estimate MMG activity, as they correlate well with muscle force. These estimations are, however, greatly affected by the presence of structured impulsive noise that overlaps in frequency with the MMG signal. In this paper, we present a method for assessing muscle activity based on the Lempel-Ziv algorithm: the Multistate Lempel-Ziv (MLZ) index. The behaviour of the MLZ index was tested with synthesized signals, with various amplitude distributions and degrees of complexity, and with recorded diaphragm MMG signals. We found that this index, like the ARV and RMS parameters, is positively correlated with changes in amplitude of the diaphragm MMG components, but is less affected by components that have non-random behaviour (like structured impulsive noise). Therefore, the MLZ index could provide more information to assess the MMG-force relationship.

  • Evaluación no invasiva de la función muscular respiratoria mediante el análisis de la señal mecanomiográfica en pacientes con enfermedad pulmonar obstructiva crónica  Open access

     Sarlabous Uranga, Leonardo
    Defense's date: 2013-10-22
    Universitat Politècnica de Catalunya
    Theses

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    El estudio y evaluación de la función muscular respiratoria en enfermedades respiratorias a través de técnicas no invasivas representa un tema de gran interés, dado que hasta la fecha no existen métodos satisfactorios aplicables en situaciones clínicas. En la enfermedad pulmonar obstructiva crónica (EPOC), el trabajo mecánico de los músculos respiratorios aumenta dando lugar a la fatiga, disminución de los movimientos de la caja torácica, y por tanto una disminución de la eficiencia muscular respiratoria. Es conocido que el músculo diafragma, principal responsable de la actividad mecánica respiratoria, al igual que otros músculos esqueléticos vibra lateralmente durante su contracción. De ahí, que estas vibraciones puedan ser registradas mediante micrófonos, sensores piezoeléctricos o acelerómetros posicionados encima de la pared inferior del pecho en la zona de aposición del diafragma con la caja torácica. El registro de estas vibraciones da lugar a la señal mecanomiográfica del diafragma (MMGdi). El principal objetivo de esta tesis ha sido el estudio y caracterización no invasiva de la función muscular respiratoria en pacientes con EPOC a través de la señal MMGdi registrada mediante acelerómetros posicionados entre el séptimo y octavo espacios intercostales, en la línea axilar izquierda y derecha del cuerpo durante la realización de los protocolos respiratorios de carga incremental progresiva y de flujo incremental progresivo. Para mejorar la estimación de la amplitud de la señal MMGdi se han propuesto tres nuevos índices, que tienen en cuenta la naturaleza aleatoria y el ruido asociado en las señales MMGdi, y están basados en: el algoritmo de Lempel-Ziv (LZM), la entropía aproximada (fApEn), y la entropía muestral (fSampEn). Todos ellos son calculados con intervalos de cuantificación fijos y empleando ventanas móviles. Los resultados obtenidos con éstos índices han permitido estimar con mayor fiabilidad y robustez la amplitud de las señales MMGdi, en relación a los métodos clásicos utilizados en el estudio de señales miográficas. El estudio del valor medio de los parámetros analizados ha mostrado, que existe una tendencia incremental de éste en los parámetros de amplitud, y una tendencia decreciente en los parámetros frecuenciales (frecuencias media y máxima), con el incremento de la carga y/o flujo. En este sentido, se ha observado que el valor medio es mayor cuanto mayor es la severidad del paciente con EPOC. Por otra parte, se ha observado que existe una fuerte correlación entre los parámetros de amplitud y la presión inspiratoria máxima en el protocolo de flujo incremental progresivo, con una tendencia decreciente con la severidad. Del mismo modo la eficiencia muscular respiratoria, evaluada como la relación entre la fuerza que producen los músculos respiratorios (la presión inspiratoria en boca) y lo que gastan o necesitan para producir esta presión (la vibración de los músculos respiratorios evaluada mediante las señales MMGdi), ha mostrado en general una tendencia decreciente con el aumento de la severidad. Finalmente, los resultados que se desprenden de esta tesis indican que el estudio de la señal MMGdi representa una herramienta útil con un gran potencial para evaluar el grado de la severidad presente en sujetos con EPOC y su relación con la debilidad de la musculatura respiratoria, y por tanto su aplicación en estudios clínicos podría ser de gran ayuda para evaluar el desarrollo de la EPOC.

    The study and evaluation of the respiratory muscles function in people who suffer from respiratory diseases can be evaluated through the use of noninvasive techniques. This is a topic of great interest considering there are currently no existing methods that can be successfully applied in clinical situations. In chronic obstructive pulmonary disease (COPD), the mechanical work of the respiratory muscles increases, which could lead to muscular fatigue, decreased movement of the ribcage, and, therefore, a decrease in the respiratory muscle efficiency. The diaphragm muscle is the principal muscle of inspiration and the main mechanical responsible for the ventilation. Similar to other skeletal muscles the diaphragm laterally vibrates during its contraction. These vibrations can be recorded by microphones, piezoelectric sensors or accelerometers, which are placed above the lower chest wall in the area of apposition of the diaphragm to the ribcage. The record of these vibrations is known as mechanomyographic signal of the diaphragm muscle (MMGdi). The main objective of this thesis has been the study and noninvasive characterization of the respiratory muscles function in patients with COPD. This characterization has been made possible through the use of MMGdi signals recorded by accelerometers placed between the seventh and eighth intercostals spaces on the left and right anterior axillary lines of the body during two respiratory protocols. The first protocol is called progressive incremental load protocol and the second one progressive incremental flow protocol. In this thesis three new indices have been proposed to improve the MMGdi amplitude estimation. These indices take into account the random nature and the associated noise in the MMGdi signals, and are based on the: Lempel-Ziv algorithm (MLZ), approximate entropy (fApEn), and sample entropy (fSampEn). All of them are calculated with fixed quantization intervals and using moving windows. The obtained results with these new indices have shown improved reliability and robustness in the MMGdi amplitude estimation in comparison with classic methods used to study myographic signals. The study of the mean value of the analyzed parameters has shown an increasing trend of the amplitude parameters and a decreasing trend of the frequency parameters (mean and maximum frequencies) with increasing load and/or flow. Furthermore, we found that there was a direct relationship between these mean values and the severity of COPD; hence, the greater the mean value, the greater the severity of COPD. Moreover, we have seen that there is a strong correlation between the amplitude parameters and the maximum inspiratory pressure in the progressive incremental flow protocol with a decreasing trend as the severity of the patients increases. Likewise, the respiratory muscle efficiency, evaluated as the ratio between the force produced by the respiratory muscles (mouth inspiratory pressure) and what they need to produce this pressure (the vibration of respiratory muscles assessed by MMGdi signals), has also shown a generally decreasing trend as the severity of patients increases. Finally, the results of this thesis suggest that the study of the MMGdi signal is a useful tool with great potential to assess the relationship between respiratory muscle weakness and the degree of severity in patients with COPD. Therefore, the application of this innovative tool in clinical studies may be helpful to assess the development of COPD.

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    Reducción de interferencia cardíaca en señales MMG diafragmáticas de un protocolo de carga incremental sostenida mediante filtrado adaptativo RLS  Open access

     Sarlabous Uranga, Leonardo; Torres Cebrian, Abel; Fiz Fernández, José A.; Jane Campos, Raimon
    Congreso Anual de la Sociedad Española de Ingeniería Biomédica
    Presentation's date: 2012-11-20
    Presentation of work at congresses

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    En este trabajo se aplicó el filtrado adaptativo empleando el algoritmo RLS para reducir la interferencia de origen cardíaco en las señales mecanomiográficas diafragmáticas (MMGdi) registradas durante un protocolo de carga incremental sostenida. La señal MMGdi fue dividida en tramos con y sin ruido cardíaco, CRC y SRC, respectivamente. En cada tramo se estudio el comportamiento de la densidad espectral de potencia (DEP), y los parámetros de amplitud RMS y ARV para cada una de las cargas inspiratorias que conforman el test. Los resultados obtenidos, empleando filtro adaptativo de orden =50, con el algoritmo RLS y valores de - = 1, permiten reducir considerablemente la interferencia cardíaca en las señales MMGdi.

  • Evaluation and adaptive attenuation of the cardiac vibration interference in mechanomyographic signals

     Sarlabous Uranga, Leonardo; Torres Cebrian, Abel; Fiz, José Antonio; Morera Prat, Josep Maria; Jane Campos, Raimon
    IEEE Engineering in Medicine and Biology Society
    Presentation's date: 2012-09-01
    Presentation of work at congresses

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    The study of the mechanomyographic signal of the diaphragm muscle (MMGdi) is a promising technique in order to evaluate the respiratory muscles effort. The relationship between amplitude and frequency parameters of this signal with the respiratory effort performed during respiration is of great interest for researchers and physicians due to its diagnostic potentials. However, MMGdi signals are frequently contaminated by a cardiac vibration or mechanocardiographic (MCG) signal. An adaptive noise cancellation (ANC) can be used to reduce the MCG interference in the recorded MMGdi activity. In this paper, it is evaluated the proposed ANC scheme by means of a synthetic MMGdi signal with a controlled MCG interference. The Pearson’s correlation coefficient (PCC) between both root mean square (RMS) and mean frequency (fm) of the synthetic MMGdi signal are considerably reduced with the presence of cardiac vibration noise (from 0.95 to 0.87, and from 0.97 to 0.76, respectively). With the ANC algorithm proposed the effect of the MCG noise on the amplitude and frequency of MMG parameters is reduced considerably (PCC of 0.93 and 0.97 for the RMS and fm, respectively). The ANC method proposed in this work is an interesting technique to attenuate the cardiac interference in respiratory MMG signals. Further investigation should be carried out to evaluate the performance of the ANC algorithm in real MMGdi signals.

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    Evaluación de diferentes algoritmos adaptativos para la atenuación de la interferencia cardiaca en señales mecanomiográficas simuladas  Open access

     Torres Cebrian, Abel; Sarlabous Uranga, Leonardo; Fiz Fernández, José A.; Jane Campos, Raimon
    Congreso Anual de la Sociedad Española de Ingeniería Biomédica
    Presentation's date: 2012-11-21
    Presentation of work at congresses

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    El estudio de la señal mecanomiográfica del músculo diafragma (MMGdi) es una técnica utilizada para evaluar el esfuerzo muscular respiratorio. El estudio de la relación entre los parámetros de amplitud y frecuencia de esta señal con el esfuerzo respiratorio realizado es de gran interés para investigadores y médicos debido a su potencial de diagnóstico sobre la función muscular respiratoria. Las señales MMGdi se ven afectas por una componente interferente correspondiente a la actividad vibratoria cardíaca o interferencia mecanocardiográfica (MCG). Para reducir o atenuar esta actividad se puede utilizar una cancelación adaptativa de interferencias (CAI). En este trabajo se ha evaluado el esquema de CAI propuesto mediante una señal MMGdi sintética generada con amplitud y frecuencia controlada a la que se le ha añadido ruido MCG real adquirido durante apnea. El coeficiente de correlación de Pearson (r) entre la amplitud y la frecuencia teóricas, y la amplitud y la frecuencia evaluadas mediante el RMS y la frecuencia media del espectro, respectivamente, disminuye considerablemente cuando se añade el ruido cardíaco a la señal MMGdi sintética: pasa de 0.95 a 0.87 para la amplitud, y de 0.97 a 0.76 para la frecuencia. Con los algoritmos de CAI propuestos el efecto del ruido MCG sobre la actividad MMGdi se reduce considerablemente (r de 0.93 para la amplitud y 0.97 para la frecuencia media). El método de CAI propuesto en este trabajo es una técnica adecuada para atenuar la interferencia MCG en señales MMGdi.

  • Evaluation of the respiratory muscles efficiency during an incremental flow respiratory test

     Sarlabous Uranga, Leonardo; Torres Cebrian, Abel; Fiz, José A.; Gea, J; Martínez-Llorens, Juana M.; Morera Prat, Josep Maria; Jane Campos, Raimon
    IEEE Engineering in Medicine and Biology Society
    Presentation's date: 2011-09-01
    Presentation of work at congresses

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    The aim of this study was to evaluate the respiratory muscles efficiency during a progressive incremental flow (IF) respiratory test in healthy and Chronic Obstructive Pulmonary Disease (COPD) subjects. To achieve this, the relationship between mouth Inspiratory Pressure (IP) increment, which is a measure of the force produced by respiratory muscles, and respiratory muscular activity increment, evaluated by means of Mechanomyografic (MMG) signals of the diaphragm muscle, was analyzed. Moreover, the correlation between the respiratory efficiency measure and the obstruction severity of the subjects was also examined. Data from two groups of subjects were analyzed. One group consisted of four female subjects (two healthy subjects and two moderate COPD patients) and the other consisted of ten male subjects (six severe and four very severe COPD patients). All subjects performed an easy IF respiratory test, in which small IP values were reached. We have found that there is an increase of amplitude and a displacement towards low frequencies in the MMG signals when the IP increases. Furthermore, it has also been found that respiratory muscles efficiency is lower when greater the obstructive severity of the patients is, and it is lower in women than in men. These results suggest that the information provided by MMG signals could be used to evaluate the muscular efficiency in healthy and COPD subjects

  • Evaluación de la eficiencia de los músculos respiratorios durante un test de flujo incremental progresivo

     Sarlabous Uranga, Leonardo; Torres Cebrian, Abel; Fiz Fernández, José A.; Gea Guiral, Joaquim; Martínez-Llorens, Juana M.; Morera Prat, Josep Maria; Jane Campos, Raimon
    Congreso Anual de la Sociedad Española de Bioingeniería
    Presentation's date: 2011-11-18
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  • Adaptive bands on EEG signals extracted with empirical mode decomposition

     Diez, Pablo F.; Laciar, Eric; Torres Cebrian, Abel; Torres, A.; Mut, Vicente A.; Avila, E.
    Latin American Congress on Biomedical Engineering
    Presentation's date: 2011
    Presentation of work at congresses

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    n this work, it has been analyzed the performance of the Empirical Mode Decomposition (EMD) of electroencephalographic (EEG) signals for classification of different mental tasks. The EMD is a suitable method for processing nonstationary and nonlinear signals, as the EEG. Moreover this method is adaptive to the signal and it is able to decompose the analyzed signal into a set of adaptive frequency bands. This is quite different from the traditional approach, where EEG signals, using a spectral analysis technique, are divided in several frequency bands with fixed bandwidth, namely, d (<4 Hz), ¿ (4-7 Hz), a (8-13 Hz), ß (14-30 Hz) and ¿ (>30 Hz). This paper presents an analysis of these adaptive bands. In order to contrast results, the proposed and the traditional methods were applied in a database of EEG signals acquired in 6 subjects performing 5 mental tasks in a Brain- Computer Interface experiment.

  • Interpretation of the approximate entropy using fixed tolerance values as a measure of amplitude variations in biomedical signals

     Sarlabous Uranga, Leonardo; Torres Cebrian, Abel; Fiz Fernández, José A.; Gea Guiral, Joaquim; Martínez Llorens, Juana María; Morera Prat, Josep Maria; Jane Campos, Raimon
    IEEE Engineering in Medicine and Biology Society
    Presentation's date: 2010-09-03
    Presentation of work at congresses

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    A new method for the quantification of amplitude variations in biomedical signals through moving approximate entropy is presented. Unlike the usual method to calculate the approximate entropy (ApEn), in which the tolerance value (r) varies based on the standard deviation of each moving window, in this work ApEn has been computed using a fixed value of r. We called this method, moving approximate entropy with fixed tolerance values: ApEnf. The obtained results indicate that ApEnf allows determining amplitude variations in biomedical data series. These amplitude variations are better determined when intermediate values of tolerance are used. The study performed in diaphragmatic mechanomyographic signals shows that the ApEnf curve is more correlated with the respiratory effort than the standard RMS amplitude parameter. Furthermore, it has been observed that the ApEnf parameter is less affected by the existence of impulsive, sinusoidal, constant and Gaussian noises in comparison with the RMS amplitude parameter.

  • An epileptic seizures detection algorithm based on the empirical mode decomposition of EEG

     OROSCO, LIA; Garces Correa, A.; Torres Cebrian, Abel; Graffigna, J.P.
    IEEE Engineering in Medicine and Biology Society
    Presentation's date: 2010-10-05
    Presentation of work at congresses

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  • Multi-Parameter Analysis of ECG and Respiratory Flow Signals to Identify Success of Patients on Weaning Trials

     Correa, Lorena; Laciar, Eric; Mut, V.; Giraldo Giraldo, Beatriz F.; Torres Cebrian, Abel
    IEEE Engineering in Medicine and Biology Society
    Presentation's date: 2010-09
    Presentation of work at congresses

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    Entropía aproximada móvil con valores de tolerancia fijos como medida de las variaciones de amplitud en señales biomédicas  Open access

     Sarlabous Uranga, Leonardo; Torres Cebrian, Abel; Fiz Fernández, José A.; Gea Guiral, Joaquim; Martínez Llorens, Juana María; Jane Campos, Raimon; Morera Prat, Josep Maria
    Congreso Anual de la Sociedad Española de Ingeniería Biomédica
    Presentation's date: 2010-11-24
    Presentation of work at congresses

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    En este trabajo se presenta un nuevo método para cuantificar las variaciones de amplitud en señales biomédicas empleando la entropía aproximada (ApEn) en ventanas móviles y con valores de tolerancia (r) fijos. Los valores límites de r se corresponden con el máximo y mínimo de la desviación estándar obtenida en todas las ventanas móviles. A esta nueva métrica se le ha denominado ApEnf: entropía aproxima con valores de r fijos. ApEnf se aplicó en señales mecanomiográficas (MMG) diafragmáticas registradas en perros, para valores de r entre 0.01 y 0.4. Los resultados obtenidos indican que al aumentar el valor de r (hasta un cierto valor) las variaciones de amplitud son mejor definidas (señales menos ruidosas), aumentando así la correlación con la señal de presión inspiratoria. Además, en presencia de ruidos de tipo impulsional, sinusoidal y gaussiano, ApEnf para valores de r medios es menos afectado que el RMS.

    Postprint (author’s final draft)

  • Noninvasive evaluation of the respiratory muscular function by means of mechanomyographic signals of the diaphragm muscle in COPD patients

     Torres Cebrian, Abel; Fiz, José Antonio; Sarlabous Uranga, Leonardo; Gea Guiral, Joaquim; Martínez Llorens, Juana María; Morera Prat, Josep Maria; Jane Campos, Raimon
    European Respiratory Society Annual Congress
    Presentation's date: 2010-09
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    Evaluación de la actividad de los músculos inspiratorios mediante señales mecanomiográficas en pacientes con EPOC durante un protocolo de carga incremental  Open access

     Torres Cebrian, Abel; Sarlabous Uranga, Leonardo; Fiz Fernández, José A.; Gea Guiral, Joaquim; Martínez Llorens, Juana María; Morera Prat, Josep Maria; Jane Campos, Raimon
    Congreso Anual de la Sociedad Española de Ingeniería Biomédica
    Presentation's date: 2010-11-24
    Presentation of work at congresses

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    El estudio de señales mecanomiográficas (MMG) de músculos respiratorios es una técnica prometedora para evaluar el esfuerzo muscular respiratorio. En este trabajo se han analizado las señales MMG del músculo diafragma derecho e izquierdo registradas en pacientes con Enfermedad Pulmonar Obstructiva Crónica (EPOC) durante un protocolo de carga incremental. La población de estudio está compuesta por un grupo de 6 pacientes con EPOC severa (FEV1>50% ref and DLCO<50% ref). Se ha obtenido una alta correlación positiva entre la presión inspiratoria máxima (PImax) desarrollada y diferentes parámetros de amplitud de las señales MMG izquierda y derecha (RMS, izquierda: 0.68±0.11 – derecha: 0.69±0.12; entropía de Rényi, izquierda: 0.73±0.10 – derecha: 0.77±0.08; Lempel-Ziv Multiestado, izquierda: 0.73±0.17 – derecha: 0.74±0.08), y una correlación negativa entre la PImax y la frecuencia máxima de la señal MMG (izquierda: -0.39±0.19 – derecha: -0.65±0.09). Además hemos encontrado que la pendiente de la evolución con el incremento de carga de los parámetros de amplitud de la señal MMG, tiene una correlación positiva con el parámetro funcional respiratorio %FEV1/FVC de los 6 pacientes EPOC analizados (RMS, izquierda: 0.38 – derecha: 0.41; entropía de Rényi, izquierda: 0.45 – derecha: 0.63; Lempel-Ziv Multiestado, izquierda: 0.39 – derecha: 0.64). Estos resultados sugieren que la información proporcionada por las señales MMG podría ser utilizada para evaluar el esfuerzo respiratorio y la eficiencia muscular en pacientes EPOC.

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    Noninvasive measurement of inspiratory muscle performance by means of diaphragm muscle mechanomyographic signals in COPD patients during an incremental load respiratory test  Open access

     Torres Cebrian, Abel; Sarlabous Uranga, Leonardo; Fiz Fernández, José A.; Gea Guiral, Joaquim; Martínez Llorens, Juana María; Morera Prat, Josep Maria; Jane Campos, Raimon
    IEEE Engineering in Medicine and Biology Society
    Presentation's date: 2010-09-03
    Presentation of work at congresses

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    The study of mechanomyographic (MMG) signals of respiratory muscles is a promising noninvasive technique in order to evaluate the respiratory muscular effort and efficiency. In this work, the MMG signal of the diaphragm muscle it is evaluated in order to assess the respiratory muscular function in Chronic Obstructive Pulmonary Disease (COPD) patients. The MMG signals from left and right hemidiaphragm were acquired using two capacitive accelerometers placed on both left and right sides of the costal wall surface. The MMG signals and the inspiratory pressure signal were acquired while the COPD patients carried out an inspiratory load respiratory test. The population of study is composed of a group of 6 patients with severe COPD (FEV1>50% ref and DLCO<50% ref). We have found high positive correlation coefficients between the maximum inspiratory pressure (IPmax) developed in a respiratory cycle and different amplitude parameters of both left and right MMG signals (RMS, left: 0.68±0.11 – right: 0.69±0.12; Rényi entropy, left: 0.73±0.10 – right: 0.77±0.08; Multistate Lempel- Ziv, left: 0.73±0.17 – right: 0.74±0.08), and negative correlation between the Pmax and the maximum frequency of the MMG signal spectrum (left: -0.39±0.19 – right: -0.65±0.09). Furthermore, we found that the slope of the evolution of the MMG amplitude parameters, as the load increases during the respiratory test, has positive correlation with the %FEV1/FVC pulmonary function test parameter of the six COPD patients analyzed (RMS, left: 0.38 – right: 0.41; Rényi entropy, left: 0.45 – right: 0.63; Multistate Lempel-Ziv, left: 0.39 – right: 0.64). These results suggest that the information provided by MMG signals could be used in order to evaluate the respiratory effort and the muscular efficiency in COPD patients.

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  • Invasive and non-invasive assessment of upper airway obstruction and respiratory effort with nasal airflow and esophageal pressure analysis during sleep  Open access

     Morgenstern de Muller, Christian Rudolf
    Defense's date: 2010-02-25
    Department of Automatic Control, Universitat Politècnica de Catalunya
    Theses

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    La estimación del esfuerzo respiratorio durante el sueño es de una importancia crítica para la identificación correcta de eventos respiratorios en los trastornos respiratorios del sueño (TRS), el diagnóstico correcto de las patologías relacionadas con los TRS y las decisiones sobre la terapia correspondiente. Hoy en día el esfuerzo respiratorio suele ser estimado mediante la polisomnografía (PSG) nocturna con técnicas imprecisas y mediante la evaluación manual por expertos humanos, lo cual es un proceso laborioso que conlleva limitaciones significativas y errores en la clasificación. El objetivo principal de esta tesis es la presentación de nuevos métodos para la estimación automático, invasiva y no-invasiva del esfuerzo respiratorio y cambios en la obstrucción de las vías aéreas superiores (VAS). En especial, la aplicación de estos métodos debería permitir, entre otras cosas, la diferenciación automática invasiva y no-invasiva de eventos centrales y obstructivos durante el sueño. Con este propósito se diseñó y se obtuvo una base de datos de PSG nocturna completamente nueva de 28 pacientes con medición sistemática de presión esofágica (Pes). La Pes está actualmente considerada como el gold-standard para la estimación del esfuerzo respiratorio y la identificación de eventos respiratorios en los TRS. Es sin embargo una técnica invasiva y altamente compleja, lo cual limita su uso en la rutina clínica. Esto refuerza el valor de nuestra base de datos y la dificultad que ha implicado su adquisición. Todos los métodos de procesado propuestos y desarrollados en esta tesis están consecuentemente validados con la señal gold-standard de Pes para asegurar su validez.En un primer paso, se presenta un sistema automático invasivo para la clasificación de limitaciones de flujo inspiratorio (LFI) en los ciclos inspiratorios. La LFI se ha definido como una falta de aumento en flujo respiratorio a pesar de un incremento en el esfuerzo respiratorio, lo cual suele resultar en un patrón de flujo respiratorio característico (flattening). Un total de 38,782 ciclos respiratorios fueron automáticamente extraídos y analizados. Se propone un modelo exponencial que reproduzca la relación entre Pes y flujo respiratorio de una inspiración y permita la estimación objetiva de cambios en la obstrucción de las VAS. La capacidad de caracterización del modelo se estima mediante tres parámetros de evaluación: el error medio cuadrado en la estimación de la resistencia en la presión pico, el coeficiente de determinación y la estimación de episodios de LFI. Los resultados del modelo son comparados a los de los dos mejores modelos en la literatura. Los resultados finales indican que el modelo exponencial caracteriza la LFI y estima los niveles de obstrucción de las VAS con la mayor exactitud y objetividad. Las anotaciones gold-standard de LFI obtenidas, fueron utilizadas para entrenar, testear y validar un nuevo clasificador automático y no-invasivo de LFI basa en la señal de flujo respiratorio nasal. Se utilizaron las técnicas de Discriminant Analysis, Support Vector Machines y Adaboost para la clasificación no-invasiva de inspiraciones con las características extraídas de los dominios temporales y espectrales de los patrones de flujo inspiratorios. Este nuevo clasificador automático no-invasivo también identificó exitosamente los episodios de LFI, alcanzando una sensibilidad de 0.87 y una especificidad de 0.85. La diferenciación entre eventos respiratorios centrales y obstructivos es una de las acciones más recurrentes en el diagnostico de los TRS. Sin embargo únicamente la medición de Pes permite la diferenciación gold-standard de este tipo de eventos. Recientemente se han propuesto nuevas técnicas para la diferenciación no-invasiva de apneas e hipopneas. Sin embargo su adopción ha sido lenta debido a su limitada validación clínica, ya que la creación manual por expertos humanos de sets gold-standard de validación representa un trabajo laborioso. En esta tesis se propone un nuevo sistema para la diferenciación gold-standard automática y objetiva entre hipopneas obstructivas y centrales. Expertos humanos clasificaron manualmente un total de 769 hypopneas en 28 pacientes para crear un set de validación gold-standard. Como siguiente paso se extrajeron características específicas de cada hipopnea para entrenar y testear clasificadores (Discriminant Analysis, Support Vector Machines y adaboost) para diferenciar entre hipopneas centrales y obstructivas mediante la señal gold-standard Pes. El sistema de diferenciación automática alcanzó resultados prometedores, obteniendo una sensibilidad, una especificad y una exactitud de 0.90. Por lo tanto este sistema parece prometedor para la diferenciación automática, gold-standard de hipopneas centrales y obstructivas. Finalmente se propone un sistema no-invasivo para la diferenciación automática de hipopneas centrales y obstructivas. Se propone utilizar la señal de flujo respiratorio para la diferenciación utilizando características de los ciclos inspiratorios de cada hipopnea, entre ellos los patrones flattening. Este sistema automático no-invasivo es una combinación de los sistemas anteriormente presentados y se valida mediante las anotaciones gold-standard obtenidas mediante la señal de Pes por expertos humanos. Los resultados de este sistema son comparados a los resultados obtenidos por expertos humanos que utilizaron un nuevo algoritmo no-invasivo para la diferenciación manual de hipopneas. Los resultados del sistema automático no-invasivo son prometedores y muestran la viabilidad de la metodología empleada. Una vez haya sido validado extensivamente, se ha propuesto este algoritmo para su utilización en dispositivos de terapia de TRS desarrollados por uno de los socios cooperantes en este proyecto.

    The assessment of respiratory effort during sleep is of major importance for the correct identification of respiratory events in sleep-disordered breathing (SDB), the correct diagnosis of SDB-related pathologies and the consequent choice of treatment. Currently, respiratory effort is usually assessed in night polysomnography (NPSG) with imprecise techniques and manually evaluated by human experts, resulting in a laborious task with significant limitations and missclassifications.The main objective of this thesis is to present new methods for the automatic, invasive and non-invasive assessment of respiratory effort and changes in upper airway (UA) obstruction. Specifically, the application of these methods should, in between others, allow the automatic invasive and non-invasive differentiation of obstructive and central respiratory events during sleep.For this purpose, a completely new NPSG database consisting of 28 patients with systematic esophageal pressure (Pes) measurement was acquired. Pes is currently considered the gold-standard to assess respiratory effort and identify respiratory events in SDB. However, the invasiveness and complexity of Pes measurement prevents its use in clinical routine, underlining the importance of this new database. . . All the processing methods developed in this thesis will consequently be validated with the gold-standard Pes-signal in order to ensure their clinical validity.In a first step, an (invasive) automatic system for the classification of inspiratory flow limitation (IFL) in the inspiratory cycles is presented.IFL has been defined as a lack of increase in airflow despite increasing respiratory effort, which normally results in a characteristic inspiratory airflow pattern (flattening). A total of 38,782 breaths were extracted and automatically analyzed. An exponential model is proposed to reproduce the relationship between Pes and airflow of an inspiration and achieve an objective assessment of changes in upper airway obstruction. The characterization performance of the model is appraised with three evaluation parameters: mean-squared-error when estimating resistance at peakpressure,coefficient of determination and assessment of IFL episodes. The model's results are compared to the two best-performing models in the literature. The results indicated that the exponential model characterizes IFL and assesses levels of upper airway obstruction with the highest accuracy and objectivity.The obtained gold-standard IFL annotations were then employed to train, test and validate a new automatic, non-invasive IFL classification system by means of the nasal airflow signal. Discriminant Analysis, Support Vector Machines and Adaboost algorithms were employed to objectively classify breaths non-invasively with features extracted from the time and frequency domains of the breaths' flow patterns. The new non-invasive automatic classification system also succeeded identifying IFL episodes, achieving a sensitivity of 0.87 and a specificity of 0.85.The differentiation between obstructive and central respiratory events is one of the most recurrent tasks in the diagnosis of sleep disordered breathing, but only Pes measurement allows the gold-standard differentiation of these events. Recently new techniques have been proposed to allow the non-invasive differentiation of hypopneas. However, their adoption has been slow due to their limited clinical validation, as the creation of manual, gold-standard validation sets by human experts is a cumbersome procedure. In this study, a new system is proposed for an objective automatic, gold-standard differentiation between obstructive and central hypopneas with the esophageal pressure signal. An overall of 769 hypopneas of 28 patients were manually scored by human experts to create a gold-standard validation set. Then, features were extracted from each hypopnea to train and test classifiers (Discriminant Analysis, Support Vector Machines and adaboost classifiers) to differentiate between central and obstructive hypopneas with the gold-standard esophageal pressure signal. The automatic differentiation system achieved promising results, with a sensitivity of 0.82, a specificity of 0.87 and an accuracy of 0.85. Hence, this system seems promising for an automatic, goldstandard differentiation between obstructive and central hypopneas.Finally, a non-invasive system is proposed for the automatic differentiation of central and obstructive hypopneas. Only the airflow signal is used for the differentiation, as features of the inspiratory cycles of the hypopnea, such as the flattening patterns, is used. The automatic, non-invasive system represents a combination of the systems that have been presented before and it was validated with the gold-standard scorings obtained with the Pes-signal by human experts. The outcome is compared to the results obtained by human scorers that applied a new non-invasive algorithm for the manual differentiation of hypopneas. The non-invasive system's results are promising and show the viability of this technique. Once validated, this algorithm has been proposed to be used in therapy devices developed by one of the partner institutions cooperating in this project.

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    Classification of mental tasks using different spectral estimation methods  Open access

     Diez, Pablo F.; Laciar, Eric; Mut, Vicente A.; Ávila, Enrique; Torres Cebrian, Abel
    Date of publication: 2009-10-01
    Book chapter

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  • Sleep apnea detection based on spectral analysis of three ECG - derived respiratory signals

     Correa, L.S.; Laciar Leber, Eric; Mut, Vicente A.; Torres Cebrian, Abel; Jane Campos, Raimon
    IEEE Engineering in Medicine and Biology Society
    Presentation's date: 2009-09-04
    Presentation of work at congresses

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    Evaluation of the respiratory muscular function by means of diaphragmatic mechanomyographic signals in COPD patients  Open access

     Sarlabous Uranga, Leonardo; Torres Cebrian, Abel; Fiz, José A.; Gea, Joaquim; Martínez-Llorens, Juana M.; Jane Campos, Raimon
    IEEE Engineering in Medicine and Biology Society
    Presentation's date: 2009-09-05
    Presentation of work at congresses

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    The study of mechanomyographic (MMG) signals of respiratory muscles is a promising technique in order to evaluate the respiratory muscular effort. In this work MMG signals from left and right hemidiaphragm (MMGl and MMGr, respectively) acquired during a respiratory protocol have been analyzed. The acquisition of both MMG signals was carried out by means of two capacitive accelerometers placed on both left and right sides of the costal wall. The signals were recorded in a group of six patients with Chronic Obstructive Pulmonary Disease (COPD). It has been observed that with the increase of inspiratory pressure it takes place an increase of the amplitude and a displacement toward low frequencies in both left and right MMG signals. Furthermore, it has been seen that the increase of amplitude and the decrease of frequency in MMG signals are more pronounced in severe COPD patients. This behaviour is similar for both MMGl and MMGr signals. Results suggest that the use of MMG signals could be potentially useful for the evaluation of the respiratory muscular function in COPD patients.

  • Application of the empirical mode decomposition to the extraction of features from EEG signals for mental task classification

     Diez, Pablo F.; Mut, Vicente A.; Laciar Leber, Eric; Torres Cebrian, Abel; Avila, E.
    IEEE Engineering in Medicine and Biology Society
    Presentation's date: 2009-09-04
    Presentation of work at congresses

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  • Interpretación del índice de Lempel-Ziv Multiestado (LZM) como medida frente a cambios de amplitud y complejidad en señales biomédicas

     Sarlabous Uranga, Leonardo; Torres Cebrian, Abel; Fiz Fernández, José A.; Gea Gurial, Joaquim; Galdiz, Juan B.; Jane Campos, Raimon
    Congreso Anual de la Sociedad Española de Ingeniería Biomédica
    Presentation's date: 2009-11-20
    Presentation of work at congresses

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    Multistate Lempel-Ziv (MLZ) index interpretation as a measure of amplitude and complexity changes  Open access

     Sarlabous Uranga, Leonardo; Torres Cebrian, Abel; Fiz, José A.; Gea, Joaquim; Galdiz, Juan B.; Jane Campos, Raimon
    IEEE Engineering in Medicine and Biology Society
    Presentation's date: 2009-09-05
    Presentation of work at congresses

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    The Lempel-Ziv complexity (LZ) has been widely used to evaluate the randomness of finite sequences. In general, the LZ complexity has been used to determine the complexity grade present in biomedical signals. The LZ complexity is not able to discern between signals with different amplitude variations and similar random components. On the other hand, amplitude parameters, as the root mean square (RMS), are not able to discern between signals with similar power distributions and different random components. In this work, we present a novel method to quantify amplitude and complexity variations in biomedical signals by means of the computation of the LZ coefficient using more than two quantification states, and with thresholds fixed and independent of the dynamic range or standard deviation of the analyzed signal: the Multistate Lempel-Ziv (MLZ) index. Our results indicate that MLZ index with few quantification levels only evaluate the complexity changes of the signal, with high number of levels, the amplitude variations, and with an intermediate number of levels informs about both amplitude and complexity variations. The study performed in diaphragmatic mechanomyographic signals shows that the amplitude variations of this signal are more correlated with the respiratory effort than the complexity variations. Furthermore, it has been observed that the MLZ index with high number of levels practically is not affected by the existence of impulsive, sinusoidal, constant and Gaussian noises compared with the RMS amplitude parameter.

  • Evaluación de la función muscular respiratoria mediante señales mecanomiográficas del músculo diafragma en pacientes con EPOC

     Torres Cebrian, Abel; Sarlabous Uranga, Leonardo; Fiz Fernández, José A.; Gea Gurial, Joaquim; Martínez Llorens, Juana María; Jane Campos, Raimon
    Congreso Anual de la Sociedad Española de Ingeniería Biomédica
    Presentation's date: 2009-11-20
    Presentation of work at congresses

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  • Rényi Entropy and Lempel-Ziv Complexity of Mechanomyographic Recordings of Diaphragm Muscle as Indexes of Respiratory Effort

     Torres Cebrian, Abel; Fernandez, J Fiz; Jane Campos, Raimon; Laciar, Eric; Galdiz, J B; Gea, J; Morera Prat, Josep Maria
    IEEE Engineering in Medicine and Biology Society
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  • Evaluación del esfuerzo muscular respiratorio mediante la entropía de Rényi y el coeficiente de complejidad de Lempel-Ziv de registros mecanomiográficos de músculos respiratorios

     Torres Cebrian, Abel; Fernández, J A Fiz; Jane Campos, Raimon; Laciar, Eric; Sarlabous, L Uranga; Gáldiz, J B Iturri; Guiral, J Gea; Morera Prat, Josep Maria
    Congreso Anual de la Sociedad Española de Ingeniería Biomédica
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  • A Comparative Study of the Performance of Different Spectral Estimation Methods for Classification of Mental Tasks

     Diez, Pablo F.; Laciar, Eric; Mut, V; Perona, E M Avila; Torres Cebrian, Abel
    IEEE Engineering in Medicine and Biology Society
    Presentation of work at congresses

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  • Performance Evaluation of Three Methods for Respiratory Signal Estimation from the Electrocardiogram

     Correa, L; Laciar, Eric; Torres Cebrian, Abel; Jane Campos, Raimon
    IEEE Engineering in Medicine and Biology Society
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  • Estudio Comparativo del Desempeño de Diferentes Métodos de Estimación de la Señal Respiratoria a partir del ECG

     Correa, L Prado; Laciar, Eric; Torres Cebrian, Abel; Jane Campos, Raimon
    Congreso Anual de la Sociedad Española de Ingeniería Biomédica
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  • Analysis of respiratory mechanomyographic signals by means of the empirical mode decomposition

     Torres Cebrian, Abel; Jane Calleja, Enrique; FIZ, J A; Galdiz, J B; Gea, J; Morera Prat, Josep Maria
    Journal of physics: conference series
    Date of publication: 2007-01
    Journal article

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  • Application of the Empirical Mode Decomposition Method to the Analysis of Respiratory Mechanomyographic Signals

     Torres Cebrian, Abel; FIZ, J A; Jane Campos, Raimon; Galdiz, J B; Gea, J; Morera Prat, Josep Maria
    IEEE Engineering in Medicine and Biology Society
    Presentation's date: 2007-08-23
    Presentation of work at congresses

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  • Aplicación del método de descomposición empírica en modos para el análisis de la señal mecanomiográfica del músculo diafragma

     Torres Cebrian, Abel
    Congreso Anual de la Sociedad Española de Ingeniería Biomédica
    Presentation's date: 2007-11-14
    Presentation of work at congresses

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  • Aplicación del método de descomposicion empírica en modos para el análisis de la señal mecanomiográfica del músculo diafragma

     Torres Cebrian, Abel; Antonio, José Fiz; Jane Campos, Raimon; Bautista, Juan; Joaquim, Gea; Morera Prat, Josep Maria
    Congreso Anual de la Sociedad Española de Ingeniería Biomédica
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  • Evaluación del esfuerzo respiratorio a partir de la entropía de Shannon de la señal mecanomiográfica del músculo diafragma

     Torres Cebrian, Abel; Fernández, J A Fiz; Gáldiz, J B Iturri; Guiral, J Gea; Morera Prat, Josep Maria; Jane Campos, Raimon
    Congreso Anual de la Sociedad Española de Ingeniería Biomédica
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  • Evaluación del esfuerzo respiratorio a partir de la entropía de Shannon de la señal mecanomiográfica del músculo diafragma

     Torres Cebrian, Abel
    Congreso Anual de la Sociedad Española de Ingeniería Biomédica
    Presentation's date: 2006-11-06
    Presentation of work at congresses

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  • Análisis de Señal Promediada y Latido a Latido del ECG de Alta Resolución en Pacientes con Mal de Chagas

     Laciar, Eric; Jane Campos, Raimon; Brooks, D H; Torres Cebrian, Abel
    Congreso Anual de la Sociedad Española de Ingeniería Biomédica
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  • Análisis de Señal Promediada y Latido a Latido del ECG de Alta Resolución en Pacientes con Mal de Chagas

     Torres Cebrian, Abel
    Congreso Anual de la Sociedad Española de Ingeniería Biomédica
    Presentation's date: 2006-11-06
    Presentation of work at congresses

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  • Detection and Adaptive Cancellation of Heart Sound Interference in Tracheal Sounds

     Torres Cebrian, Abel
    IEEE Engineering in Medicine and Biology Society
    Presentation's date: 2006-08-30
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  • Detection and Adaptive Cancellation of Heart Sound Interference in Tracheal Sounds

     Cortes Rubiano, Sandra; Jane Campos, Raimon; Torres Cebrian, Abel; Fernandez, José Antonio Fiz; Morera Prat, Josep Maria
    IEEE Engineering in Medicine and Biology Society
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  • Cancelación adaptativa de la interferencia del sonido cardiaco en el sonido respiratorio

     Torres Cebrian, Abel
    Congreso Anual de la Sociedad Española de Ingeniería Biomédica
    Presentation's date: 2006-11-06
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  • Inspiratory Pressure Evaluation by means of the Entropy of Respiratory Mechanomyographic Signals

     Torres Cebrian, Abel; Fernandez, José Antonio Fiz; Bautista, Juan Galdiz; Joaquim, Gea; Morera Prat, Josep Maria; Jane Campos, Raimon
    IEEE Engineering in Medicine and Biology Society
    Presentation's date: 2006-08-30
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  • Cancelación adaptativa de la interferencia del sonido cardiaco en el sonido respiratorio

     Cortes Rubiano, Sandra; Jane Campos, Raimon; Torres Cebrian, Abel; Fernández, J A Fiz; Morera Prat, Josep Maria
    Congreso Anual de la Sociedad Española de Ingeniería Biomédica
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  • Separación de las componentes de alta y baja frecuencia de señales mecanomiográficas mediante un método wavelet multiescala

     Torres Cebrian, Abel; FIZ, J A; Galdiz, B; Gea, J; Morera Prat, Josep Maria; Jane Campos, Raimon
    Congreso Anual de la Sociedad Española de Ingeniería Biomédica
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  • A Wavelet Multiscale Based Method to Separate the High and Low Frequency Components of Mechanomyographic Signals

     Torres Cebrian, Abel; Fernandez, José Antonio Fiz; Bautista, Juan Galdiz; Joaquim, Gea; Morera Prat, Josep Maria; Jane Campos, Raimon; Mañanas Villanueva, Miguel Angel
    IEEE Engineering in Medicine and Biology Society
    Presentation's date: 2005-09-01
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  • Separación de las componentes de alta y baja frecuencia de señales mecanomiográficas mediante un método wavelet multiescala

     Torres Cebrian, Abel
    Congreso Anual de la Sociedad Española de Ingeniería Biomédica
    Presentation's date: 2005-11-10
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  • Non-Invasive monitoring of diaphragmatic timing by means of surface contact sensors: An experimental study in dogs

     FIZ, J A; Jane Campos, Raimon; Torres Cebrian, Abel; Morera Prat, Josep Maria; Galdiz, B; Gea, J; Grassino, A
    BMC pulmonary medicine (Online)
    Date of publication: 2004-09
    Journal article

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