A novel artifact reconstruction method applied to blood pressure signals

Peer ReviewedPostprint (published version

Characterization of the microvascular cerebral blood flow response to obstructive apneic events during night sleep

Peer ReviewedPostprint (author's final draft

Contribución al diagnóstico autómatico de arritmias cardíacas basado en el código minnesota

El objetivo de esta tesis se enmarca en el diseño y desarrollo de un sistema automático de ayuda al diagnostico de arritmias cardiacas, denominado Saydac, que comprende: la caracterización del ECG, que permite generar su descripción en forma cualitativa y cuantitativa; la detección y el diagnostico de la fibrilación y el fluter auriculares a través de la detección de las ondas F del registro electrocardiográfico; la descripción y codificación de las arritmias cardiacas basado en el código Minnesota, y la validación de Saydac para la cual se han obtenido los diagnósticos de 8 evaluadores (3 médicos cardiólogas expertos en arritmias, 3 médicos cardiólogos, 1 medico no cardiólogo y Saydac) para un total de 100 señales electrocardiográficas efectuándose luego un análisis estadístico de las diferentes distancias entre los diagnostico de cada uno de los evaluadores. Se ha constatado que Saydac responde satisfactoriamente a los objetivos de su diseño, con diagnósticos más próximos a los médicos cardiólogos especialistas en arritmias que al resto de evaluadores

Cardiorespiratory phase synchronization increases during certain mental stimuli in healthy subjects

Several neurological and mechanical non-linear mechanisms relate the respiratory and cardiovascular systems to one another. Besides the well-known modulation of heart rate by respiration, another form of non-linear interaction between both systems is Cardiorespiratory Phase Synchronization (CRPS). In this study we investigated CRPS on a group of 27 healthy individuals subject to a stimulation protocol with five different mental states: a basal state, a videogame, a comedy video, a suspense video and a reading state. A continuous measure of CRPS was calculated from the phase synchrogram between respiratory and electrocardiographic signals. Periods of CRPS were characterized by their average duration (AvDurSync) and by the percentage of synchronized time (%Sync) within each mental state. These measures were studied considering two thresholds: a minimum amplitude and a minimum duration for synchronization. Each subject exhibited a particular pattern of phase locking ratios along the different mental states. We observed that, in all states, %Sync decreased and AvDurSync increased in proportion to the minimum duration threshold. Both measures were inversely proportional to the minimum amplitude threshold. During the videogame, subjects showed a significantly higher %Sync as compared to any other mental stimulus, irrespective of the minimum duration threshold. Mental stimulation can be an alternative approach to enhance cardiorespiratory coupling when subjects have difficulties to perform aerobic exercise, such as in patients with Chronic Obstructive Pulmonary Disease or Chronic Heart failure.Peer ReviewedPostprint (author's final draft

Caracterización de pacientes con diferentes niveles de riesgo cardiovascular mediante diagramas de Poincaré

En este trabajo se propone caracterizar la dinámica no-lineal de los sistemas cardíaco, vascular y respiratorio a partir de los diagramas de Poincaré. Se han analizado 46 pacientes con cardiomiopatía isquémica (ICM) o dilatada (DCM), y 35 sujetos sanos. De acuerdo con su fracción de eyección ventricular izquierda (LVEF), los pacientes también fueron clasificados en un grupo de alto riesgo (HR: LVEF = 35%, 30 pacientes) y otro de bajo riesgo (LR: LVEF > 35%, 16 pacientes). A partir de las señales electrocardiográfica, de flujo respiratorio y de presión sanguínea se han obtenido los datos relacionados con el tiempo entre latidos cardíacos (RR), entre valores máximos de presión sistólica (SBP), y la duración del ciclo respiratorio (TTot). Estas series temporales han sido representadas mediante los diagramas de Poincaré, y caracterizadas teniendo en cuenta su desviación a largo plazo (SD1) y su cambio instantáneo (SD2). De acuerdo con los resultados obtenidos, los parámetros de las series cardíaca y de presión sanguínea, relacionados con las diagonales longitudinales y transversales del diagrama de Poincaré, son los que mejor diferencian entre pacientes con HR vs LR. Para la clasificación de pacientes isquémicos vs dilatados, los mejores parámetros se obtuvieron a partir de las series respiratorias y están relacionados con las distancias de la desviación estándar a la línea de identidad. Los cambios en estas relaciones representan una mayor aceleración en la dinámica respiratoria de los pacientes con cardiomiopatía isquémica.Postprint (published version

La insuficiencia cardíaca crónica en pacientes ancianos

Debido al creciente número de personas de edad avanzada y al extenso número de comorbilidades que les afectan, se requieren estudios para planificar los futuros incrementos en el número de ingresos en los servicios clínicos, y en particular en los de urgencias. Algunos de los problemas clínicos más comunes en pacientes ancianos están relacionados con enfermedades de los sistemas cardiovascular y respiratorio. Los pacientes ancianos a menudo presentan alteraciones en el patrón respiratorio, como son la respiración periódica (PB) y la respiración Cheyne-Stokes (CSR), que puede coincidir con una insuficiencia cardíaca crónica. El estudio de la envolvente de la señal respiratoria es un claro indicador de la modulación del patrón respiratorio

Belowground productivity of mangrove forests in southwest Florida

Studies in belowground dynamics are limited mainly due to the difficulty of studying roots despite wide recognition of its importance. This dissertation focused on methods for analyzing mangrove roots, root responses to phosphorus and flooding, and variation in root production between forest types. Techniques to separate live and dead roots such as colorimetric, fluorescence, buoyancy, and visual assessment were compared. The traditional method of visual assessment combined with root buoyancy was accurate, fast, and applicable to larger samples. Additionally, techniques such as rhizotrons, root ingrowth cores, and root image analysis were useful to study mangrove roots. Root and litter production, and hydro-edaphic conditions were determined seasonally for one year at eight sites (fringe, basin, and scrub forest types) in Southwest Florida. Root production was equal or greater than litter production showing spatial variation, especially in biomass allocation. Correlations with soil variables indicated that above and belowground processes respond differently to environmental conditions. The combined root+litter production was a good predictor of flooding and nutrient stress. Mangrove root production and morphology responded to nutrient enrichment (additions of nitrogen or phosphorus) depending upon forest type and stress factors interacting with resource acquisition. Root production increased with low nutrient availability and high flooding, and decreased with high salinity and nutrient availability. Nutrient enrichment increased the specific root length and surface area at the basin-monospecific site, and decreased the specific surface area at the scrub forest. Greenhouse experiments were conducted to study root dynamics of Rhizophora mangle and Avicennia germinans seedlings in response to phosphorus availability and flooding regimes. Mangrove species differed in their tolerance of flooding, and their plasticity to nutrients availability. The more flood tolerant species, R. mangle, was slower growing. The faster-growing species, A. germinans, exhibited limitations to flooding and changes in root morphology that altered the surface area for absorption of nutrients. These results indicate a trade-off between root strategies to tolerate flooding and to acquire nutrients. This study contributes to a better understanding of how mangrove ecosystems function. Additional work in other geographic areas and sedimentary settings is needed to provide a broader perspective on belowground processes in mangrove systems

BARRANCO SECO Y BOMBEO MOYA [Material gráfico]

Copia digital. Madrid : Ministerio de Educación, Cultura y Deporte, 201

Using the heart rate variability for classifying patients with and without chronic heart failure and periodic breathing

Assessment of the dynamic interactions between cardiovascular signals can provide valuable information that improves the understanding of cardiovascular control. Heart rate variability (HRV) analysis is known to provide information about the autonomic heart rate modulation mechanism. Using the HRV signal, we aimed to obtain parameters for classifying patients with and without chronic heart failure (CHF), and with periodic breathing (PB), non-periodic breathing (nPB), and Cheyne-Stokes respiration (CSR) patterns. An electrocardiogram (ECG) and a respiratory flow signal were recorded in 36 elderly patients: 18 patients with CHF and 18 patients without CHF. According to the clinical criteria, the patients were classified into the follow groups: 19 patients with nPB pattern, 7 with PB pattern, 4 with Cheyne-Stokes respiration (CSR), and 6 non-classified patients (problems with respiratory signal). From the HRV signal, parameters in the time and frequency domain were calculated. Frequency domain parameters were the most discriminant in comparisons of patients with and without CHF: PTOT, PLF and fpHF. For the comparison of the nPB vs CSR patients groups, the best parameters were RMSSD and SDSD. Therefore, the parameters appear to be suitable for enhanced diagnosis of decompensated CHF patients and the possibility of developed periodic breathing and a CSR pattern

Respiratory sinus arrhythmia quantified with linear and non-linear techniques to classify dilated and ischemic cardiomyopathy

Peer ReviewedPostprint (author's final draft