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Aquest treball de fi de grau es centra en el disseny d'un dispositiu no invasiu per diferenciar entre persones diabètiques i no diabètiques mitjançant l'anàlisi del comportament cardíac. L'objectiu principal és comprendre com la diabetis afecta la freqüència cardíaca, així com desenvolupar un dispositiu electrònic capaç de discriminar basant-se en les mesures de la freqüència cardíaca. S'ha examinat la conveniència d'utilitzar l'electrocardiografia (ECG) o la fotopletismografia (PPG) per a aquest propòsit, amb un enfocament específic en el disseny de hardware i deixant la part de software per a futures investigacions. La PPG s'ha presentat com l'opció preferida degut al confort dels pacients, malgrat que fan falta estudis pràctics per corroborar-ho. A més, s'ha analitzat la base de dades DICARDIA per investigar els efectes en la freqüència cardíaca en persones diabètiques, tant amb com sense condicions cardiovasculars preexistents, durant proves d'esforç. Els resultats indiquen una disminució significativa en les freqüències cardíaques i en la recuperació de la freqüència cardíaca en persones diabètiques, coincidint amb les expectatives inicials., Este trabajo de fin de grado se centra en el diseño de un dispositivo no invasivo para diferenciar entre personas diabéticas y no diabéticas mediante el análisis del comportamiento cardíaco. El objetivo principal es comprender cómo la diabetes afecta la frecuencia cardíaca y desarrollar un dispositivo electrónico capaz de discriminar basándose en el ritmo cardíaco. Se evaluó la conveniencia de utilizar la electrocardiografía (ECG) o la fotopletismografía (PPG) para este propósito, centrándose específicamente en el diseño de hardware y dejando el software para futuras investigaciones. La PPG se presenta como la opción preferida debido a la comodidad del paciente, aunque son necesarios estudios prácticos para corroborarlo. Además, se analizó la base de datos DICARDIA para investigar los efectos en la frecuencia cardíaca en personas diabéticas, tanto con como sin condiciones cardiovasculares preexistentes, durante pruebas de esfuerzo. Los resultados indican una disminución significativa en las frecuencias cardíacas y en la recuperación de la frecuencia cardíaca en personas diabéticas, lo cual concuerda con las expectativas iniciales., This final degree project focuses on designing a non-invasive device to differentiate between diabetic and non-diabetic individuals by analysing their cardiac behaviour. The primary goal is to understand how diabetes affects heart rate and to develop an electronic device for effective discrimination based on heart rate measurements. It is assessed the suitability of electrocardiography (ECG) or photoplethysmography (PPG) for this purpose, with a specific focus on hardware design, leaving the software aspect for future research. PPG emerges as the preferred choice due to the comfortability given to the patient, however practical studies are needed to prove it fully. Furthermore, DICARDIA database was examined to investigate how diabetes impacts heart rate in individuals, both with and without pre-existing cardiovascular conditions, during exercise stress tests. The results indicate significantly lower heart rates and heart rate recovery in diabetic individuals, aligning with initial expectations.

To recognize and assess the job stressors that teachers face in daily practice is essential. One of the most used objective measures of stress is the heart rate (HR). This pilot study explored the use of a wearable device (smartwatch) to monitor the HR of two teachers over two weeks in the classroom. Educational context variables (subject, class size, timetable, activity learning performed) and environment variables (temperature, humidity, sun irradiance) were related with HR. The results showed significant differences on HR among the teachers according to the educational activity, time of the day, or day of the week. The environmental variables were related differently in each of the participants. The study showed the practical implications of using a smartwatch, or smart bracelet, in the field of education. It provides systematic data that be analyzed and linked to other variables, opening the possibility of measuring real-time stress in the classroom, as an alternative or complement to stress self-reports, Peer Reviewed

Blood testing has traditionally been the gold standard for the physiological analysis and monitoring of professional athletes. In recent years, blood testing has moved out of the laboratory thanks to portable handheld devices, such as lactate meters. However, despite its usefulness and widespread use, blood testing has several drawbacks and limitations, such as the need for the athlete to stop exercising for blood extraction and the inability to have data continuously collected. In this scenario, sweat has become an alternative to blood testing because of its rich content of electrolytes and metabolites, as well as small quantities of sugars, proteins, and ions. Nevertheless, there are few devices capable of analyzing this biofluid and providing useful information to users. In this paper, an electronic system designed for the autonomous analysis of sweat electrolytes and metabolites along with heart rate dynamics is presented. This system is part of a novel wearable device tailored for athletes that offers to the user a real-time assessment of their physiological status and performance, This work was supported by the Spanish Ministerio de Indústria, Energía y Turismo, grant numbers AEI-010500-2020-198 and AEI-010500-2022b-111, and AGAUR, grant numbers 2019 DI 18 and 2019 DI 29, Postprint (published version)

L’estudi de l’activitat cardíaca en fetus és una eina vital per conèixer i monitorar la resposta del cor a diferents estímuls i, el comportament d’altres sistemes que l’afecten, com el sistema nerviós. Un dels paràmetres més emprats per estudiar el cor és la variabilitat del ritme cardíac (Heart Rate Variability, HRV). Existeixen diferents dispositius que permeten obtenir la freqüència cardíaca fetal, i conseqüentment, la HRV. En el present treball, s’ha fet ús d’un micròfon connectat a la sortida d’un cardiotocògraf per registrar els sons cardíacs d’un fetus. Aquest projecte té com a objectiu analitzar l’activitat cardíaca fetal per estudiar la influència de diferents estímuls auditius en forma de veu. S’han emprat diferents mètodes de processament de senyals per obtenir els paràmetres referents a la HRV, com per exemple filtrar, interpolar, calcular l’envolupant i la densitat espectral de potència. Els resultats obtinguts permeten analitzar el comportament cardíac d’un fetus influenciat per una veu externa. Els paràmetres temporals de la HRV augmenten a mesura que avança el registre, és a dir que la variabilitat del ritme cardíac creix. A la vegada, hi ha un canvi de predominança de la banda de freqüència. En un inici, la HF presenta una major potència, fet que es veu invertit cap al final del registre fonogràfic. Aquest fet s’assimila a què el fetus passa d’estar en repòs a estar actiu, però relaxat, i cap al final de la prova, sembla que es comença a estressar. Els resultats obtinguts s'han de contrastar en una base de dades major, que permeti determinar si aquests resultats són generalitzables, i analitzar si hi ha altres factors que puguin influenciar la resposta cardíaca del fetus., El estudio de la actividad cardíaca en fetos es una herramienta vital para conocer y monitorizar la respuesta del corazón a diferentes estímulos y, el comportamiento de otros sistemas que le afectan, como el sistema nervioso. Uno de los parámetros más empleados para estudiar el corazón es la variabilidad del ritmo cardíaco (Heart Rate Variability, HRV). Existen diferentes dispositivos que permiten obtener la frecuencia cardíaca fetal y, por tanto, la HRV. En el presente trabajo se ha utilizado un micrófono conectado a la salida de un cardiotocógrafo para registrar los sonidos cardíacos de un feto. Este proyecto tiene como objetivo analizar la actividad cardíaca fetal para estudiar la influencia de diferentes estímulos auditivos en forma de voz. Se han empleado diferentes métodos de procesamiento de señales para obtener los parámetros referentes a la HRV, como por ejemplo filtrar, interpolar, calcular el envolvente y la densidad espectral de potencia. Los resultados obtenidos permiten analizar el comportamiento cardíaco de un feto influenciado por una voz externa. Los parámetros temporales de la HRV aumentan a medida que avanza el registro, es decir, la variabilidad del ritmo cardíaco aumenta. A su vez, hay un cambio de predominancia de la banda de frecuencia. En un inicio, la HF presenta una mayor potencia, factor que se ve invertido en el final del registro fonográfico. Este hecho se asimila a que el feto pasa de estar en reposo a estar activo, pero relajado, y al final de la prueba, parece que se empieza a estresar. Los resultados obtenidos se deben contrastar en una base de datos mayor, que permita determinar si estos resultados son generalizables, y analizar si hay otros factores que puedan influir en la respuesta cardíaca del feto., The study of cardiac activity in fetuses is a vital tool for understanding and monitoring the response of the heart to different stimuli and the behavior of other systems that affect it, such as the nervous system. One of the most commonly used parameters to study the heart is the Heart Rate Variability (HRV). There are different devices that allow obtaining the fetal heart rate, and consequently, the HRV. In the present work, a microphone connected to the output of a cardiotocograph has been used to record the heart sounds of a fetus. The aim of this project is to analyze fetal cardiac activity in order to study the influence of different auditory stimuli in the form of a voice. Different signal processing methods have been used to obtain the HRV parameters, such as filtering, interpolation, calculation of the envelope and power spectral density. The results obtained allow us to analyze the cardiac behavior of a fetus influenced by an external voice. The time parameters of the HRV increase as the recording progresses, i.e., the variability of the heart rate increases. At the same time, there is a change in the predominance of the frequency band. Initially, HF presents a greater power, a fact that is reversed towards the end of the phonographic recording. This is likened to the fetus going from being at rest to being active, but relaxed, and at the end of the test, it appears to start to become stressed. The results obtained should be checked against a large database to determine whether these results are generalizable, and to analyze whether there are other factors that may influence the fetal cardiac response.

Intermittent hypoxia (IH) produces autonomic dysfunction that promotes the development of arrhythmia and hypertension in patients with obstructive sleep apnea (OSA). This paper investigated different heart rate variability (HRV) indices in the context of IH using a rat model for OSA. Linear and non-linear HRV parameters were assessed from ultra-short (15-s segments) and short-term (5 min) analyses of heartbeat time-series. Transient changes observed from pre-apnea segments to hypoxia episodes were evaluated, besides the relative and global impact of IH, as a function of its severity. Results showed an overall increase in ultra-short HRV markers as immediate response to hypoxia: standard deviation of normal RR intervals, SDNN = 1.2 ms (IQR: 1.1-2.1) vs 1.4 ms (IQR: 1.2-2.2), p = 0.015; root mean square of the successive differences, RMSSD = 1.7 ms (IQR: 1.5-2.2) vs 1.9 ms (IQR: 1.6-2.4), p = 0.031. The power in the very low frequency (VLF) band also showed a significant increase: 0.09 ms 2 (IQR: 0.05-0.20) vs 0.16 ms 2 (IQR: 0.12-0.23), p = 0.016, probably associated with the potentiation of the carotid body chemo-sensory response to hypoxia. Moreover, a clear link between severity of IH and short-term HRV measures was found in VLF and LF power, besides their progressive increase seen throughout the experiment after each apnea sequence. However, only those markers quantifying fragmentation levels in RR series were significantly affected when the experiment ended, as compared to baseline measures: percentage of inflection points, PIP = 49% (IQR: 45-51) vs 53% (IQR: 47-53), p = 0.031; percentage of short (geq 3 RR intervals) accelerated/decelerated segments, PSS = 75% (IQR: 51-81) vs 87% (IQR: 51-90), p = 0.046. These findings suggest a significant deterioration of cardiac rhythm with a more erratic behavior beyond the normal sinus arrhythmia, that may lead to a future cardiac condition., Peer Reviewed, Postprint (published version)

Chronic obstructive pulmonary disease (COPD) patients exhibit impaired autonomic control which can be assessed by heart rate variability analysis. The study aims to evaluate the cardiac autonomic responses of COPD patients after completing a conventional six-minute walk test (6MWT). Fifty COPD patients were included in the study, for which an ECG signal (lead II) was acquired by a wearable device, before, during, and after the test. We used the heart rate (HR) time-series to assess the heart rate dynamic during recovery. The heart rate recovery (HRR) marker was evaluated every 5 s after the 6MWT and showed different dynamic trends among severity groups. We compared the HRR among patient groups classified according to the GOLD standard. Significantly larger normalized HRR values (nHRR) were found in mild COPD patients (n=23, GOLD={1,2}; nHRR1=14.8±7.5 %, nHRR2=18.6±8.1 %) compared to those with more disease severity (n=23, GOLD={3,4}; nHRR1=9.3±5.8 %, p=0.002; and nHRR2= 13.7±6.7 %, p=0.041). The largest differences were observed around the first 30 s of the recovery phase (nHRR=10.8±6.6 % vs. nHRR=5.6±4 % p=0.001). Our results showed a slower recovery for the severest patients, suggesting that cardiac parameters like the ones we propose here, may provide valuable information for a better characterization of COPD severity., Peer Reviewed, Postprint (published version)

© 2019 Elsevier. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0, A measurement method of heart rate and heart rate variability (HRV) based on smartphone has been developed and validated. The method is based on photoplethysmography (PPG) acquired with the smartphone camera (SPPG). SPPG was compared with the electrocardiogram (ECG), used as the gold standard, and with an external PPG sensor. Twenty-three healthy subjects were measured using two different smartphone models in three different breathing conditions. The error of the first differentiation between SPPG and ECG series is minimized with the fiducial point at maximum first derivative of the SPPG. The obtained standard deviation of error (SDE) between SPPG and ECG is around 5.4 ms and it is similar to SDE between PPG and ECG. Good agreement between SPPG and ECG for NN, SDNN and RMSSD have been found but it is insufficient agreement for LF/HF. Similar levels of agreement for SPPG-ECG and PPG-ECG have been obtained for the HRV indices. Finally, the differences between smartphone models for HRV indices are slight. Therefore, the smartphone can be used for measuring accurately the following HRV indices: NN, SDNN and RMSSD., Peer Reviewed, Postprint (published version)

© 2019 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting /republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works, Developing a tool which identifies emotions based on their effect on cardiac activity may have a potential impact on clinical practice, since it may help in the diagnosing of psycho-neural illnesses. In this study, a method based on the analysis of heart rate variability (HRV) guided by respiration is proposed. The method was based on redefining the high frequency (HF) band, not only to be centered at the respiratory frequency, but also to have a bandwidth dependent on the respiratory spectrum. The method was first tested using simulated HRV signals, yielding the minimum estimation errors as compared to classical and respiratory frequency centered at HF band based definitions, independently of the values of the sympathovagal ratio. Then, the proposed method was applied to discriminate emotions in a database of video-induced elicitation. Five emotional states, relax, joy, fear, sadness and anger, were considered. The maximum correlation between HRV and respiration spectra discriminated joy vs. relax, joy vs. each negative valence emotion, and fear vs. sadness with p-value = 0.05 and AUC = 0.70. Based on these results, human emotion characterization may be improved by adding respiratory information to HRV analysis., Peer Reviewed, Postprint (author's final draft)

© 2019 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting /republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works, In this paper, a non-linear HRV analysis was performed to assess fragmentation signatures observed in heartbeat time series after intermittent hypoxia (IH). Three markers quantifying short-term fragmentation levels, PIP, IALS and PSS, were evaluated on R-R interval series obtained in a rat model of recurrent apnea. Through airway obstructions, apnea episodes were periodically simulated in six anesthetized Sprague-Dawley rats. The number of apnea events per hour (AHI index) was varied during the first half of the experiment while apnea episodes lasted 15 s. For the second part, apnea episodes lasted 5, 10 or 15 s, but the AHI index was fixed. Recurrent apnea was repeated for 15-min time intervals in all cases, alternating with basal periods of the same duration. The fragmentation markers were evaluated in segments of 5 minutes, selected at the beginning and end of the experiment. The impact of the heart and breathing rates (HR and BR, respectively) on the parameter estimates was also investigated. The results obtained show a significant increase (from 5 to 10%, p <; 0.05) in fragmentation measures of heartbeat time series after IH, indicating a clear deterioration of the initial conditions. Moreover, there was a strong linear relationship (r > 0.9) between these markers and BR, as well as with the ratio given by HR/BR. Although fragmentation may be impacted by IH, we found that it is highly dependent on HR and BR values and thus, they should be considered during its calculation or used to normalize the fragmentation estimates, Peer Reviewed, Postprint (published version)

Objective: This works investigates the time-frequency content of impedance cardiography signals during a propofol-remifentanil anesthesia. Materials and Methods: In the last years, impedance cardiography (ICG) is a technique which has gained much attention. However, ICG signals need further investigation. Time-Frequency Distributions (TFDs) with 5 different kernels are used in order to analyze impedance cardiography signals (ICG) before the start of the anesthesia and after the loss of consciousness. In total, ICG signals from one hundred and thirty-one consecutive patients undergoing major surgery under general anesthesia were analyzed. Several features were extracted from the calculated TFDs in order to characterize the time-frequency content of the ICG signals. Differences between those features before and after the loss of consciousness were studied. Results: The Extended Modified Beta Distribution (EMBD) was the kernel for which most features shows statistically significant changes between before and after the loss of consciousness. Among all analyzed features, those based on entropy showed a sensibility, specificity and area under the curve of the receiver operating characteristic above 60%. Conclusion: The anesthetic state of the patient is reflected on linear and non-linear features extracted from the TFDs of the ICG signals. Especially, the EMBD is a suitable kernel for the analysis of ICG signals and offers a great range of features which change according to the patient’s anesthesia state in a statistically significant way., Peer Reviewed, Postprint (author's final draft)

Purpose This study was conducted to test, in mountain running route conditions, the accuracy of the Polar V800™ monitor as a suitable device for monitoring the heart rate variability (HRV) of runners. Method Eighteen healthy subjects ran a route that included a range of running slopes such as those encountered in trail and ultra-trail races. The comparative study of a V800 and a Holter SEER 12 ECG Recorder™ included the analysis of RR time series and short-term HRV analysis. A correction algorithm was designed to obtain the corrected Polar RR intervals. Six 5-min segments related to different running slopes were considered for each subject. Results The correlation between corrected V800 RR intervals and Holter RR intervals was very high (r¿=¿0.99, p¿<¿0.001), and the bias was less than 1 ms. The limits of agreement (LoA) obtained for SDNN and RMSSD were (-¿0.25 to 0.32 ms) and (-¿0.90 to 1.08 ms), respectively. The effect size (ES) obtained in the time domain HRV parameters was considered small (ES¿<¿0.2). Frequency domain HRV parameters did not differ (p¿>¿0.05) and were well correlated (r¿=¿0.96, p¿<¿0.001). Conclusion Narrow limits of agreement, high correlations and small effect size suggest that the Polar V800 is a valid tool for the analysis of heart rate variability in athletes while running high endurance events such as marathon, trail, and ultra-trail races., Peer Reviewed, Postprint (author's final draft)

The aim of the study was to analyze heart rate variability (HRV) response to high-intensity exercise during a 35-km mountain trail race and to ascertain whether fitness level could influence autonomic nervous system (ANS) modulation. Time-domain, frequency-domain, and multi-scale entropy (MSE) indexes were calculated for eleven mountain-trail runners who completed the race. Many changes were observed, mostly related to exercise load and fatigue. These changes were characterized by increased mean values and standard deviations of the normal-to-normal intervals associated with sympathetic activity, and by decreased differences between successive intervals related to parasympathetic activity. Normalized low frequency (LF) power suggested that ANS modulation varied greatly during the race and between individuals. Normalized high frequency (HF) power, associated with parasympathetic activity, varied considerably over the race, and tended to decrease at the final stages, whereas changes in the LF/HF ratio corresponded to intervals with varying exercise load. MSE indexes, related to system complexity, indicated the existence of many interactions between the heart and its neurological control mechanism. The time-domain, frequency-domain, and MSE indexes were also able to discriminate faster from slower runners, mainly in the more difficult and in the final stages of the race. These findings suggest the use of HRV analysis to study cardiac function mechanisms in endurance sports, Peer Reviewed, Postprint (author's final draft)

© 2017 by the authors. The aim of the study was to analyze heart rate variability (HRV) response to high-intensity exercise during a 35-km mountain trail race and to ascertain whether fitness level could influence autonomic nervous system (ANS) modulation. Time-domain, frequency-domain, and multi-scale entropy (MSE) indexes were calculated for eleven mountain-trail runners who completed the race. Many changes were observed, mostly related to exercise load and fatigue. These changes were characterized by increased mean values and standard deviations of the normal-to-normal intervals associated with sympathetic activity, and by decreased differences between successive intervals related to parasympathetic activity. Normalized low frequency (LF) power suggested that ANS modulation varied greatly during the race and between individuals. Normalized high frequency (HF) power, associated with parasympathetic activity, varied considerably over the race, and tended to decrease at the final stages, whereas changes in the LF/HF ratio corresponded to intervals with varying exercise load. MSE indexes, related to system complexity, indicated the existence of many interactions between the heart and its neurological control mechanism. The time-domain, frequency-domain, and MSE indexes were also able to discriminate faster from slower runners, mainly in the more difficult and in the final stages of the race. These findings suggest the use of HRV analysis to study cardiac function mechanisms in endurance sports., Peer Reviewed, Postprint (author's final draft)

Emotions are directly related whit external or internal stimulation which a person is submitted, influencing these stimuli on their physical and mental health. These emotional changes produce variations in cardiovascular behavior and respiratory activity. This research proposes the characterization of cardiac system in healthy subject submitted to 3 different audiovisual stimuli, by means of the analysis of Heart Rate Variability (HRV) and upward and downward slopes of the QRS complex. The electrocardiographic signal (3 leads) was recorded from 29 healthy subjects. An audiovisual stimulation protocol was designed. Principal characteristic of ECG signals were extracted. After, a model was designed based on a Fuzzy K Nearest Neighbors classifier to determine different cardiac patterns related to each stimulus. Two classification procedure were performed, the first comparing all groups of stimuli, and the second comparing each pair of stimuli. These comparisons were applied to each obtained characteristic, HRV, and slopes. According to the results, HRV was able to differentiate between basal state and fear, with an area under the curve of 79%. Finally, two new healthy subjects were analysed with the obtained model. The pattern used with HRV and the upward slope of QRS showed clear differences between the propose stimuli., Postprint (published version)

Background: Optimization of cardiac output (CO) has been evidenced to reduce postoperative complications and to expedite the recovery. Likewise, CO and other dynamic cardiac parameters can describe the systemic blood flow and tissue oxygenation state and can be useful in different clinical fields. This study aimed to validate the qCO monitor (Quantium Medical, Barcelona, Spain), a new device to estimate CO and other related parameters in a continuous, fully non-invasive way using advanced digital signal processing of impedance cardiography. Methods: The LiDCOrapidv2 (LiDCO Ltd, London, UK) was used to compare the performance of the qCO in 15 patients during major surgery under general anesthesia. Full surgeries were recorded and cardiac output obtained by both devices was compared by using correlation and Bland-Altman analysis. Results: The Bland-Altman analysis showed sufficient agreement with a mean bias of -0.03 ± 0.71 L/min. Conclusions: The findings showed that both systems offered comparable values and thus the non-invasive measurement of CO with qCO is a promising, feasible method. Further investigation will be required to validate this new device against calibrated devices and outcome studies would also be highly recommended., Postprint (author's final draft)

This work proposes a systematic procedure to report the differences between heart rate variability time series obtained from alternative measurements reporting the spread and mean of the differences as well as the agreement between measuring procedures and quantifying how stationary, random and normal the differences between alternative measurements are. A description of the complete automatic procedure to obtain a differences time series (DTS) from two alternative methods, a proposal of a battery of statistical tests, and a set of statistical indicators to better describe the differences in RR interval estimation are also provided. Results show that the spread and agreement depend on the choice of alternative measurements and that the DTS cannot be considered generally as a white or as a normally distributed process. Nevertheless, in controlled measurements the DTS can be considered as a stationary process., Peer Reviewed, Postprint (published version)

Electromechanical alternans is a beat-to-beat alternation in the strength of contraction of a cardiac cell, which can be caused by an instability of calcium cycling. Using a distributed model of subcellular calcium we show that alternans occurs via an order-disorder phase transition which exhibits critical slowing down and a diverging correlation length. We apply finite size scaling along with a mapping to a stochastic coupled map model, to show that this transition in two dimensions is characterized by critical exponents consistent with the Ising universality class. These findings highlight the important role of cooperativity in biological cells, and suggest novel approaches to investigate the onset of the alternans instability in the heart., Peer Reviewed, Postprint (author’s final draft)

Determinar les característiques de bombeig d'un cor com a bomba volumétrica.Simular comportament cor sa, incloent-hi dinámica de vàlvules i l'evolució dels volums durant un cicle. Avaluar l'efecte de determinades cardiopaties comunicants sobre el bombeig. Ampliar simulació i fer-ne anàlisi.Introduir efectes no lineals i propietats reològiques reals de la sang., En l’actualitat, el nombre d’investigacions i de projectes realitzats amb la col·laboració de diverses disciplines de la ciència i la tecnologia és més elevat. Per tal de trobar equacions o lleis genèriques que permetin definir la realitat, cada vegada més es requereix un conjunt de coneixements de diversos àmbits. En el cas del present estudi, es pretén fer un anàlisi comparatiu de la capacitat de bombeig del cor en condicions normals i quan es presenten algunes cardiopaties congènites. Per assolir-ho, s’ha emprat els sistemes Bondgraph que permeten definir qualsevol realitat com un conjunt d’elements interconnectats entre si que dissipen energia, n’emmagatzemen, etc. Els resultats obtinguts obren les portes a assajar altres cardiopaties congènites o patologies cardiovasculars., Nowadays researches and projects that include all kind of science and technology disciplines are increasing in number. In order to find equations or general laws that can define reality, knowledge in several fields is increasingly required. In the case of this study, the aim is to make a comparative analysis of the pumping ability of the human heart between normal conditions and some congenital heart diseases. To do so, Bondgraph systems have been considered the best option because they allow to represent the reality as a set of interconnected elements which can dissipate energy, keep energy, etc. The obtained results lead to try other congenital heart diseases or some other cardiovascular diseases.

Motion compensation constitutes a challenging issue in minimally invasive beating heart surgery. Since the zone to be repaired has a dynamic behaviour, precision and surgeon's dexterity decrease. In order to solve this problem, various proposals have been presented using l2-norm. However, as they present some limitations in terms of robustness and efficiency, motion compensation is still considered an open problem. In this work, a solution based on the class of l1-Regularized Optimization is proposed. It has been selected due to its mathematical properties and practical benefits. In particular, deformation is characterized by cubic B-splines since they offer an excellent balance between computational cost and accuracy. Moreover, due to the non-differentiability of the functional, the logarithmic barrier function is used for generating a standard optimization problem. Results have provided a very good trade-off between accuracy and efficiency, indicating the potential of the proposed approach and proving its stability even under complex deformations., Peer Reviewed, Postprint (published version)

Fractional differintegration is used as a new tool to characterize heart rate variability time series. This paper proposes and focuses in two indexes (ac and fnQ) derived from the fractional differintegration operator. Both indexes are applied to fractional Gaussian noise (fGn) and actual RR time series in order to test their behavior. In the analysis of monofractal time series, ac is linearly related with the Hurst exponent and the estimation of the exponent by the proposed index has lower variance than by using Detrended Fluctuation Analysis (DFA) or the periodogram. The other index fnQ quantifies how the time series adjust to a monofractal time series. Age, postural changes and paced breathing cause significant changes on fnQ while ac only shows significant changes due to posture. In the analyzed actual HRV time series, ac shows good correlation with the short term scaling exponent obtained by DFA, LF/HF and RMSSD while no correlations have been found for fnQ., Peer Reviewed, Postprint (published version)

The study aimed to study the accuracy in RR time series derived from the seismocardiogram when employing different heartbeat detectors in subjects measured in a quiet environment. The ECG and seismocardiogram of 17 healthy volunteers was recorded at a sampling frequency of 5 kHz using a Biopac acquisition system. The seismocardiogram was acquired using a triaxial accelerometer (LIS344ALH, ST Microelectronics). Four detectors of the heartbeat from the seismocardiogram were employed relying either on the Continuous Wavelet Transform or bandpass filtering. The detectors adapt their parameters to the morphology of the signal by estimating mean heart rate and the bandwidth of the signal associated to the heartbeat. For all detectors, the standard deviation of the error in the obtained RR time series is in mean slightly higher than 2 ms and the percentage of obtained RR time intervals that have an error higher than 30 ms is around 3.5%. The seismocardiogram, when measured in a quiet environment, can be used instead of the ECG to obtain reliable RR time series when using proper heartbeat detectors., Peer Reviewed, Postprint (published version)

The study aims to present and interpret a novel index based on fractional calculus ( αc) and to assess differences in RR time series dynamics in subjects during meditation. Fractional differintegration (FDI) of a RR time series provides a new time series.αc is defined as the order of the FDI operator that provides the time series with minimum variance. Analyzed time series were obtained from the Exaggerated Heart Rate Oscillations During Two Meditation Techniques database. This database contains RR time series before and after Chi Meditation and Kundalini Yoga. It also contains recordings of elite athletes and healthy subjects while sleeping and during metronomic breathing at 0.25 Hz. αc is significantly higher during Chi or Yoga meditation when compared with the recordings before the meditation starts or in subjects while sleeping or during metronomic breathing.

Heart Rate Variability (HRV) is an indicator of health status in the general population and of adaptatio n to stress in athletes. In this paper we compare the performance of two systems to measure HRV: (1) A commercial system based on recording the physiological cardiac signal with (2) A computer vision system that uses a standard video images of the face to estimate RR from changes in skin color of the face. We show that the computer vision system performs surprisingly well. It estimates individual RR intervals in a non - invasive manner and with error levels comparable to those achieved by the physiological based system., Peer Reviewed, Postprint (published version)

The objective of this project is to identify the peripheral heart rate in the arm or hand, using dry electrodes and an impedance converter monolithic, by bioimpedance measures. To perform the project, first has been characterized impedance converter. (we used the AD5933 from Analog Devices). Different possibilities have been raised for signal conditioning, seeing the viability of each one. Once you have found which responded to the objectives of the project is described in depth. For interaction with the user has designed a Visual Basic program that performs the data capture for post processing. Finally, we show the results of the measures taken in the arm and hand.

Results of heart rate variability analysis depend on the quality of the initial RR time series that is measured only in one lead of the ECG. This work shows that RR time series can subtly change from lead to lead so the choice of the analyzed lead is another source of uncertainty. The standard deviation of the differences of two RR time series obtained from different leads can change from 0.5 ms to more than 20 ms depending on the amount of noise, the morphological changes of the QRS complexes, the strategies of fiducial point determination and the measured subject. This source of uncertainty is in healthy subjects greater than that associated to the sampling frequency of the ECG for sampling frequencies greater than 400 Hz., Peer Reviewed, Postprint (published version)

The aim of this study is to determine the changes in heart rate variability (HRV) in field hockey players during the course of a world championship. The Spanish national team took part in the study by making daily records of the R-R interval (Omegawave System) on the days when matches took place. The baseline heart rate (HR) and several parameters of HRV were measured. The evolution of the average values of the HR and the various parameters of HRV during the 7 matches was compared using a MANOVA, the contrasts regarding the last match being analysed. The HR increases progressively during the seven matches, with an especially significant increase in the last match (F(18.6) = 3.27; p=.024). RMSSD and pNN50 parameters progressively decrease throughout the tournament, with an especially significant decrease for pNN50 (F(18.6) = 2.96; p=.034). Regarding the parameters of the frequency spectrum, LF and LF/HF show an increase throughout the 7 matches (for LF, F(18.6) = 2.72; p=.046), and HF presented lower values. HRV decreases progressively and the values of the parameters related to parasympathetic system activity (RMSSD and HF) reduce, which are indicative of good psychic-physical adaptability to the workload. At the same time, the value of the parameters related to sympathetic system activity (LF and LF/HF) increases, suggesting an increase in fatigue, tiredness and poor adaptability in general. Consequently, the analysis of HRV may be a good marker for monitoring the psychic-physical state, cardiovascular adaptability during exercise and a possible state of physical overload in athletes participating in competitions., Peer Reviewed, Postprint (published version)

A major challenge of cardiac tissue engineering is directing cells to establish the physiological structure and function of the myocardium being replaced. In native heart, pacing cells generate electrical stimuli that spread throughout the heart causing cell membrane depolarization and activation of contractile apparatus. We ought to examine whether electrical stimulation of adipose tissue-derived progenitor cells (ATDPCs) exerts phenotypic and genetic changes that enhance their cardiomyogenic potential., Peer Reviewed, Postprint (published version)

Ventilatory thresholds (VT1 and VT2) are useful in many fields of medicine and sports. Nevertheless, their measurement is cumbersome and needs trained personnel. This work proposes an alternative method to predict VT1, VT2 and maximum loads in incremental maximal tests based on heart rate variability (HRV) analysis. Twelve competitive male cyclists executed an incremental exhaustive test. During the test, RR time series and gas concentrations were recorded. After artifact correction the power spectrum was estimated in a sliding window, and central frequency (CF) and bandwidth that contains half the total power (BW) were computed. An automatic algorithm recognized the loads where CF and BW undergo a significant change. These loads were used as inputs in linear regression models to predict VT1, VT2 and maximum loads. The errors of the predictions are similar to the load resolution., Postprint (published version)

Projecte final de carrera realitzat en col.laboració amb l'Illinois Institute of Technology, The use of technology in medical applications has expanded tremendously in the last 50 years, playing an important role in diagnosis and treatment of disease. As a consequence of this growth, it has been possible to develop new techniques and processes which allows scientists and physicians to extract potentially life-saving information by peering noninvasively into the human body. One of these techniques, Magnetic Resonance Imaging, has the capacity of providing data which contain information about motion of human tissue. In this project we exploit this characteristic to present a model for estimating left ventricular heart motion through a whole cardiac cycle. The model is based on the utilization of a non-rigid deformable mesh which tracks the intensity variations on the datasets of MRI images. The use of a mesh allows us to interpolate the motion on every point of the myocardial tissue. Although still in his first steps of development, preliminary results here presented demonstrate great potential of our model in terms of efficiency and flexibility versus the other existing models. It constitutes a good alternative for developing full 4D heart models in the future.

QT interval decreases with increasing heart rate (HR), hence to define normal values of QT interval for different heart rates requires the application of a QT interval rate correction formula. However, the influence of HR on the ratios between several ventricular repolarization intervals, that can be useful as risk predictors of malignant ventricular arrhythmias is unknown. This study analyzes the influence of HR on QTp/QT, JTp/JT, Tpe/JTp, and Tpe/JT ratios on a healthy subject during exercise. The intervals were measured in V3 lead and the characteristic points of QRS complex and T wave were detected by computer algorithms based on the wavelet transform (WT). Exercise stress was graded according to the four initial stages of the Bruce protocol. The heart rate was divided into two ranges: less than 100 beats/min and from 100 beats/min to 185 beats/min. When HR exceeded 100 beats/min, QTp/QT and JTp/JT ratios increased whereas Tpe/JTp and Tpe/JT ratios decreased for increasing HR. However, when HR was below 100 beats/min, those same four ratios were independent from HR. As opposed to the QT interval, there is no need to correct QTp/QT, JTp/JT, Tpe/JTp, and Tpe/JT ratios when HR is below 100 beats/min, Peer Reviewed

This paper shows that variations in breathing patterns broaden heart rate variability (HRV) spectral bands and increase the power amplitude of low-frequency bands. Because of these influences, spectral markers for HRV signals, such as the quotient between spectral power at different frequency bands, should be compared only under controlled breathing conditions or after considering the effect of variations in breathing patterns, Peer Reviewed