Relación entre la presión inspiratoria pico y la activación mecánica de los músculos inspiratorios durante respiración tranquila en pacientes con EPOC

En la enfermedad pulmonar obstructiva crónica (EPOC) la fuerza muscular inspiratoria (FMI) y la eficiencia mecánica de los músculos inspiratorios (EMMI) podrían verse reducidas como consecuencia de la hiperinsuflación. En este trabajo se registraron la presión inspiratoria en boca (PIpico) y la activación mecánica de los músculos inspiratorios en 10 pacientes EPOC severos y muy severos, durante respiración tranquila. Para determinar la activación mecánica de los músculos inspiratorios se empleó la señal mecanomiográfica diafragmática: MMGdi. La amplitud de la señal MMGdi fue estimada a través de índices lineales (ARV: valor rectificado medio) y no lineales (MLZ: Lempel-Ziv multiestado, y fSampEn: entropía muestral con valores de tolerancia fijos). Nuestra hipótesis es que el ratio entre PIpico, que refleja la FMI, y la amplitud de la señal MMGdi constituye una expresión de la EMMI. Los resultados obtenidos muestran ligeras diferencias entre la PIpico registrada en EPOC severos y muy severos, así como una correlación débil a moderada con los parámetros de función pulmonar y los índices estudiados. Sin embargo, mientras mayor es el grado de severidad (que supone un mayor grado de hiperinsuflación) mayor es el nivel de activación mecánica de los músculos inspiratorios. La activación mecánica de los músculos inspiratorios y la EMMI estimadas mediante MLZ estuvieron mejor correlacionadas con la función pulmonar que ARV y fSampEn. Por consiguiente, la estimación de la actividad mecánica del diafragma mediante el MLZ de la señal MMGdi podría mejorar la estimación no invasiva de la FMI y la EMMI, incluso para niveles muy bajos de esfuerzo inspiratorio.Peer ReviewedPostprint (author’s final draft

Evaluación de la actividad de los músculos inspiratorios mediante señales mecanomiográficas en pacientes con EPOC durante un protocolo de carga incremental

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.Postprint (published version

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

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

Producción de aromáticos por despolimerización reductiva de lignina sobre catalizadores carbonosos producidos a partir de lignosulfonato sódico.

El incremento de la producción de lignina en la industria de la producción de pasta de celulosa y en las biorefinerías lignocelulósicas, junto con la creciente demanda de procesos con cero producción de residuos en el marco de la bioeconomía circular, hace necesario desarrollar nuevas metodologías para la valorización de la lignina. Este trabajo propone su doble valorización mediante su conversión en catalizadores basados en carbono y la aplicación de éstos en su despolimerización reductiva para la producción de monómeros aromáticos de alto valor añadido. Los carbones activados empleados como soporte catalítico fueron preparados por activación química de un lignosulfonato de sodio con H3PO4 en relación 3/1 (masa agente activante/precursor carbonoso) y activados a 500 °C. El carbón activado fue impregnado con distintas cantidades de sales precursoras de níquel, molibdeno y cobalto y sometido a tratamiento térmico a 800 °C, produciendo un catalizador de níquel y dos catalizadores bimetálicos de Ni-Mo, y Co-Mo. La despolimerización reductiva de lignina organosolv se llevó a cabo empleando estos catalizadores en un reactor discontinuo agitado a 350 °C y 100 bar de presión inicial de H2 durante 4 horas. En todas las reacciones se obtuvo una fase gaseosa, una líquida orgánica, una líquida acuosa y una sólida, las cuales fueron caracterizadas a través de diferentes técnicas. El catalizador carbonoso con Ni y Mo fue el más activo, despolimerizando en gran medida la lignina, y mostrando una moderada actividad en la hidrodesoxigenación de los correspondientes monoméros aromáticos en condiciones suaves. La fase líquida orgánica obtenida presentó un alto rendimiento hacia los monoméros y elevada selectividad hacia aromáticos oxigenados de alto valor económico, como los alquilfenoles. Además, en las pruebas de reacción utilizando como materia prima otra lignina de alto contenido de azufre, el catalizador mantuvo su actividad.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Evaluation of the respiratory muscular function by means of diaphragmatic mechanomyographic signals in copd patients

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.Peer ReviewedPostprint (published version

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

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.Peer ReviewedPostprint (author’s final draft

Evaluation of the respiratory muscular function by means of diaphragmatic mechanomyographic signals in copd patients

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.Peer Reviewe

Efficiency of mechanical activation of inspiratory muscles in COPD using sample entropy

Respiratory muscle dysfunction is a common problem in patients with chronic obstructive pulmonary disease (COPD) and has mostly been related to pulmonary hyperinflation [1, 2]. Associated diaphragm shortening and deleterious changes in the muscle force-length relationship cause a reduction in the muscles’ capacity to generate pressure, placing them at a mechanical disadvantage [1, 3]. Specifically, both inspiratory muscle strength and mechanical efficiency may be reduced in COPD patients [1, 4–6], although, at iso-volume, the contractile strength of the diaphragm in COPD is preserved or may even be improved in some cases [7]. The ratio between transdiaphragmatic pressure and electrical diaphragm activity has been used as a measure of respiratory muscle efficiency [8, 9]. However, in clinical practice, it is complex to measure this parameter directly, as invasive measures are required and these are uncomfortable for patients [4]. During contraction, respiratory muscle fibres vibrate laterally [10]. These vibrations are related to the mechanical activation of these muscles and can be non-invasively recorded through accelerometers positioned on the surface of the skin, proximal to the muscles: this is called respiratory muscle mechanomyogram (MMG) [11–13]. The analysis of the mechanical activation of inspiratory muscles through the MMG might be a useful alternative approach for assessing respiratory muscles function in patients with COPD [13, 14]. MMG reflects the mechanical counterpart of the neural activity measured by electromyography. Respiratory muscle MMG provide some advantages over surface diaphragmatic electromyography with regards to simplicity of use. First of all, MMG recording is easy and simple to implement: MMG is acquired using a small accelerometer attached to the skin surface, whereas electromyography typically uses three electrodes. Secondly, as it is a mechanical signal, MMG is not susceptible to bioelectrical interference. Furthermore, the signal to noise ratio of MMG is typically higher than that of the electromyography, requiring less amplification and electrical shielding. In addition, the MMG recording does not require skin preparation and it is not influenced by changes in the skin impedance. The aim of the present study was to noninvasively evaluate the mechanical activation of inspiratory muscles and its efficiency (EMMG) during tidal volume breathing in patients with severe-to-very severe COPD. With this in mind, we investigated the peak inspiratory mouth pressure (IPpeak) and respiratory muscle MMG acquired under both quiet breathing (QB) and maximal voluntary ventilation (MVV) conditions during an incremental respiratory flow protocol

Inspiratory muscle activation increases with COPD severity as confirmed by non-invasive mechanomyographic analysis

There is a lack of instruments for assessing respiratory muscle activation during the breathing cycle in clinical conditions. The aim of the present study was to evaluate the usefulness of the respiratory muscle mechanomyogram (MMG) for non-invasively assessing the mechanical activation of the inspiratory muscles of the lower chest wall in both patients with chronic obstructive pulmonary disease (COPD) and healthy subjects, and to investigate the relationship between inspiratory muscle activation and pulmonary function parameters. Both inspiratory mouth pressure and respiratory muscle MMG were simultaneously recorded under two different respiratory conditions, quiet breathing and incremental ventilatory effort, in 13 COPD patients and 7 healthy subjects. The mechanical activation of the inspiratory muscles was characterised by the non-linear multistate Lempel–Ziv index (MLZ) calculated over the inspiratory time of the MMG signal. Subsequently, the efficiency of the inspiratory muscle mechanical activation was expressed as the ratio between the peak inspiratory mouth pressure to the amplitude of the mechanical activation. This activation estimated using the MLZ index correlated strongly with peak inspiratory mouth pressure throughout the respiratory protocol in both COPD patients (r = 0.80, p<0.001) and healthy (r = 0.82, p<0.001). Moreover, the greater the COPD severity in patients, the greater the level of muscle activation (r = -0.68, p = 0.001, between muscle activation at incremental ventilator effort and FEV1). Furthermore, the efficiency of the mechanical activation of inspiratory muscle was lower in COPD patients than healthy subjects (7.61±2.06 vs 20.42±10.81, respectively, p = 0.0002), and decreased with increasing COPD severity (r = 0.78, p<0.001, between efficiency of the mechanical activation at incremental ventilatory effort and FEV1). These results suggest that the respiratory muscle mechanomyogram is a good reflection of inspiratory effort and can be used to estimate the efficiency of the mechanical activation of the inspiratory muscles. Both, inspiratory muscle activation and inspiratory muscle mechanical activation efficiency are strongly correlated with the pulmonary function. Therefore, the use of the respiratory muscle mechanomyogram can improve the assessment of inspiratory muscle activation in clinical conditions, contributing to a better understanding of breathing in COPD patients.Peer Reviewe

Efficiency of mechanical activation of inspiratory muscles in COPD using sample entropy

Respiratory muscle dysfunction is a common problem in patients with chronic obstructive pulmonary disease (COPD) and has mostly been related to pulmonary hyperinflation [1, 2]. Associated diaphragm shortening and deleterious changes in the muscle force-length relationship cause a reduction in the muscles’ capacity to generate pressure, placing them at a mechanical disadvantage [1, 3]. Specifically, both inspiratory muscle strength and mechanical efficiency may be reduced in COPD patients [1, 4–6], although, at iso-volume, the contractile strength of the diaphragm in COPD is preserved or may even be improved in some cases [7]. The ratio between transdiaphragmatic pressure and electrical diaphragm activity has been used as a measure of respiratory muscle efficiency [8, 9]. However, in clinical practice, it is complex to measure this parameter directly, as invasive measures are required and these are uncomfortable for patients [4]. During contraction, respiratory muscle fibres vibrate laterally [10]. These vibrations are related to the mechanical activation of these muscles and can be non-invasively recorded through accelerometers positioned on the surface of the skin, proximal to the muscles: this is called respiratory muscle mechanomyogram (MMG) [11–13]. The analysis of the mechanical activation of inspiratory muscles through the MMG might be a useful alternative approach for assessing respiratory muscles function in patients with COPD [13, 14]. MMG reflects the mechanical counterpart of the neural activity measured by electromyography. Respiratory muscle MMG provide some advantages over surface diaphragmatic electromyography with regards to simplicity of use. First of all, MMG recording is easy and simple to implement: MMG is acquired using a small accelerometer attached to the skin surface, whereas electromyography typically uses three electrodes. Secondly, as it is a mechanical signal, MMG is not susceptible to bioelectrical interference. Furthermore, the signal to noise ratio of MMG is typically higher than that of the electromyography, requiring less amplification and electrical shielding. In addition, the MMG recording does not require skin preparation and it is not influenced by changes in the skin impedance. The aim of the present study was to noninvasively evaluate the mechanical activation of inspiratory muscles and its efficiency (EMMG) during tidal volume breathing in patients with severe-to-very severe COPD. With this in mind, we investigated the peak inspiratory mouth pressure (IPpeak) and respiratory muscle MMG acquired under both quiet breathing (QB) and maximal voluntary ventilation (MVV) conditions during an incremental respiratory flow protocol