Daniel Alvarez

Daniel Alvarez
Río Hortega University Hospital, Valladolid (Spain) · Sleep-Ventilation Unit, Pneumology Service

PhD

About

160
Publications
19,456
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2,702
Citations
Additional affiliations
March 2005 - August 2015
University of Valladolid
Position
  • Researcher

Publications

Publications (160)
Conference Paper
Previous studies have suggested that the typical slow oscillations (SO) characteristics during sleep could be modified in the presence of pediatric obstructive sleep apnea (OSA). Here, we evaluate whether these modifications are significant and if they may reflect cognitive deficits. We recorded the overnight electroencephalogram (EEG) of 294 pedia...
Article
The gold standard approach to diagnose obstructive sleep apnea (OSA) in children is overnight in-lab polysomnography (PSG), which is labor-intensive for clinicians and onerous to healthcare systems and families. Simplification of PSG should enhance availability and comfort, and reduce complexity and waitlists. Airflow (AF) and oximetry (SpO2) signa...
Article
Full-text available
Pulse oximetry is routinely used to non-invasively monitor oxygen saturation levels. A low oxygen level in the blood means low oxygen in the tissues, which can ultimately lead to organ failure. Yet, contrary to heart rate variability measures, a field which has seen the development of stable standards and advanced toolboxes and software, no such st...
Article
Objectives: To analyze the association between atmospheric levels of nitrogen dioxide (NO2) and the number of visits by adults to an emergency department (ED) for exacerbated asthma in an urban area with low levels of air pollution. Material and methods: Retrospective ecological time-series study. We quantified ED visits for asthma by consecutiv...
Article
Full-text available
Pediatric obstructive sleep apnea (OSA) is a prevalent disorder that disrupts sleep and is associated with neurocognitive and behavioral negative consequences, potentially hampering the development of children for years. However, its relationships with sleep electroencephalogram (EEG) have been scarcely investigated. Here, our main objective was to...
Article
Overnight pulse oximetry has shown usefulness to simplify obstructive sleep apnea (OSA) diagnosis when combined with machine-learning approaches. However, the development and evaluation of a single model with ability to reach high diagnostic performance in both community-based non-referral and clinical referral cohorts are still pending. Since ense...
Conference Paper
Sleep staging is of paramount importance in children with suspicion of pediatric obstructive sleep apnea (OSA). Complexity, cost, and intrusiveness of overnight polysomnography (PSG), the gold standard, have led to the search for alternative tests. In this sense, the photoplethysmography signal (PPG) carries useful information about the autonomous...
Article
Study Objectives Pediatric obstructive sleep apnea (OSA) affects cardiac autonomic regulation, altering heart rate variability (HRV). Although changes in classical HRV parameters occur after OSA treatment, they have not been evaluated as reporters of OSA resolution. Specific frequency bands (named BW1, BW2 and BWRes) have been recently identified i...
Article
Full-text available
Pediatric obstructive sleep apnea (OSA) is a breathing disorder that alters heart rate variability (HRV) dynamics during sleep. HRV in children is commonly assessed through conventional spectral analysis. However, bispectral analysis provides both linearity and stationarity information and has not been applied to the assessment of HRV in pediatric...
Article
Objectives: To compare the prognostic value of 3 severity scales: the Pneumonia Severity Index (PSI), the CURB-65 pneumonia severity score, and the Severity Community-Acquired Pneumonia (SCAP) score. To build a new predictive model for in-hospital mortality in patients over the age of 75 years admitted with pneumonia due to the coronavirus disease...
Article
Objective: Chronic obstructive pulmonary disease (COPD) is a highly prevalent chronic condition. COPD is a major cause of morbidity, mortality and healthcare costs globally. Spirometry is the gold standard test for a definitive diagnosis and severity grading of COPD. However, a large proportion of individuals with COPD are undiagnosed and untreate...
Article
Background Machine‐learning approaches have enabled promising results in efforts to simplify the diagnosis of pediatric obstructive sleep apnea (OSA). A comprehensive review and analysis of such studies increase the confidence level of practitioners and healthcare providers in the implementation of these methodologies in clinical practice. Objecti...
Article
Full-text available
This study focused on the automatic analysis of the airflow signal (AF) to aid in the diagnosis of pediatric obstructive sleep apnea (OSA). Thus, our aims were: (i) to characterize the overnight AF characteristics using discrete wavelet transform (DWT) approach, (ii) to evaluate its diagnostic utility, and (iii) to assess its complementarity with t...
Article
Pediatric Obstructive Sleep Apnea (OSA) is a respiratory disease whose diagnosis is performed through overnight polysomnography (PSG). Since it is a complex, time-consuming, expensive, and labor-intensive test, simpler alternatives are being intensively sought. In this study, bispectral analysis of overnight airflow (AF) signal is proposed as a pot...
Article
This study aims at assessing the usefulness of deep learning to enhance the diagnostic ability of oximetry in the context of automated detection of pediatric obstructive sleep apnea (OSA). A total of 3196 blood oxygen saturation (SpO2) signals from children were used for this purpose. A convolutional neural network (CNN) architecture was trained us...
Article
Full-text available
Positional obstructive sleep apnea (POSA) is a major phenotype of sleep apnea. Supine-predominant positional patients are frequently characterized by milder symptoms and less comorbidity due to a lower age, body mass index, and overall apnea-hypopnea index. However, the bradycardia-tachycardia pattern during apneic events is known to be more severe...
Preprint
Full-text available
Objective: Chronic obstructive pulmonary disease (COPD) is a highly prevalent chronic condition. COPD is a major source of morbidity, mortality and healthcare costs. Spirometry is the gold standard test for a definitive diagnosis and severity grading of COPD. However, a large proportion of individuals with COPD are undiagnosed and untreated. Given...
Conference Paper
Full-text available
En este estudio se evalúa la utilidad de una arquitectura deep learning basada en módulos Inception para mejorar la capacidad diagnóstica de la señal de saturación de oxígeno en sangre (SpO2) en la ayuda al diagnóstico de la apnea obstructiva del sueño (AOS) infantil. Estudios recientes demandan la aplicación de nuevas arquitecturas de deep learnin...
Conference Paper
Full-text available
Este estudio se centra en el análisis automático de la señal de flujo aéreo monocanal (FA) para la ayuda en el diagnóstico de la Apnea Obstructiva del Sueño (AOS) infantil. En concreto, se ha evaluado la utilidad diagnóstica de las medidas extraídas de los diferentes niveles de descomposición obtenidos al aplicar la transformada wavelet discreta a...
Conference Paper
Full-text available
El objetivo de este estudio fue evaluar la utilidad de la transformada wavelet de las señales de flujo aéreo (FA) y saturación de oxígeno en sangre (SpO2) para detectar la apnea obstructiva del sueño (AOS) infantil. Para ello, se emplearon las señales de 974 sujetos pediátricos con sospecha de padecer AOS, que se dividieron aleatoriamente en conjun...
Article
Background: Classic spectral analysis of heart rate variability (HRV) in pediatric sleep apnea-hypopnea syndrome (SAHS) traditionally evaluates the very low frequency (VLF: 0-0.04 Hz), low frequency (LF: 0.04-0.15 Hz), and high frequency (HF: 0.15- 0.40 Hz) bands. However, specific SAHS-related frequency bands have not been explored. Methods: 1,738...
Article
Full-text available
Introducción. El aislamiento impuesto durante la pandemia de COVID-19 podría influir en la adherencia a las terapias, especialmente en enfermos crónicos. El objetivo del estudio consistió en analizar el grado de cumplimiento de pacientes con síndrome de apnea obstructiva del sueño (SAOS) en tratamiento domiciliario con presión positiva continua (CP...
Conference Paper
In this study, we use the overnight blood oxygen saturation (SpO2) signal along with convolutional neural networks (CNN) for the automatic estimation of pediatric sleep apnea-hypopnea syndrome (SAHS) severity. The few preceding studies have focused on the application of conventional feature extraction methods to obtain information from the SpO2 sig...
Article
Full-text available
The reference standard to diagnose pediatric Obstructive Sleep Apnea (OSA) syndrome is an overnight polysomnographic evaluation. When polysomnography is either unavailable or has limited availability, OSA screening may comprise the automatic analysis of a minimum number of signals. The primary objective of this study was to evaluate the complementa...
Article
Full-text available
The most appropriate physiological signals to develop simplified as well as accurate screening tests for obstructive sleep apnoea (OSA) remain unknown. This study aimed at assessing whether joint analysis of at-home oximetry and airflow recordings by means of machine-learning algorithms leads to a significant diagnostic performance increase compare...
Article
Background and objective: In-laboratory overnight polysomnography (PSG) is the gold standard method to diagnose the sleep apnoea-hypopnoea syndrome (SAHS). PSG is a complex, expensive, labour-intensive and time-consuming test. Consequently, simplified diagnostic methods are desirable. We propose the analysis of the airflow (AF) signal by means of r...
Chapter
One major risk of paediatric sleep apnoea-hypopnoea syndrome (SAHS) is the development of cognitive impairments among affected children. Electroencephalography (EEG) is ordinarily used as part of polysomnography, the standard diagnostic test for SAHS. However, how SAHS changes overnight EEG, and its relationships with cognitive performance, remains...
Conference Paper
Pediatric sleep apnea-hypopnea syndrome (SAHS) is a highly prevalent breathing disorder that is related to many negative consequences for the children's health and quality of life when it remains untreated. The gold standard for pediatric SAHS diagnosis (overnight polysomnography) has several limitations, which has led to the search for alternative...
Conference Paper
The sleep apnea-hypopnea syndrome (SAHS) is a chronic respiratory disorder of high prevalence among children (up to 4%). Nocturnal polysomnography (PSG) is the gold standard method to diagnose SAHS, which is a complex, expensive, and time-consuming test. Consequently, alternative simplified methods are demanded. We propose the analysis of the respi...
Conference Paper
RATIONALE. Obstructive sleep apnea (OSA) in children is a highly prevalent disease that hampers their cognitive development while also increasing the risk of behavioral disturbances. Sleep fragmentation and intermittent hypoxia have been implicated in these adverse outcomes. Even though EEG is used to evaluate sleep architecture during polysomnogra...
Chapter
Full-text available
This study focuses on the at-home Sleep apnea-hypopnea syndrome (SAHS) severity estimation. Three percent oxygen desaturation index \( (ODI_{3} ) \) from nocturnal pulse-oximetry has been commonly evaluated as simplified alternative to polysomnography (PSG), the standard in-hospital diagnostic test. However, \( ODI_{3} \) has shown limited ability...
Article
Full-text available
Chronic obstructive pulmonary disease (COPD) is one of the most prevalent lung diseases worldwide. COPD patients show major dysfunction in cardiac autonomic modulation due to sustained hypoxaemia, which has been significantly related to higher risk of cardiovascular disease. Obstructive sleep apnoea syndrome (OSAS) is a frequent comorbidity in COPD...
Article
Full-text available
Complexity, costs, and waiting lists issues demand a simplified alternative for sleep apnea-hypopnea syndrome (SAHS) diagnosis. The blood oxygen saturation signal (SpO2) carries useful information about SAHS and can be easily acquired from overnight oximetry. In this study, SpO2 single-channel recordings from 320 subjects were obtained at patients’...
Article
Full-text available
Background. The gold standard for pediatric sleep apnea hypopnea syndrome (SAHS) is overnight polysomnography, which has several limitations. Thus, simplified diagnosis techniques become necessary. Objective. The aim of this study is twofold: (i) to analyze the blood oxygen saturation (SpO2) signal from nocturnal oximetry by means of features from...
Data
Actual AHI from PSG and values of all the extracted features from the SpO2 signal (ODI3, statistical moments, PSD, and DWT features) of each subject in the optimization set. (XLSX)
Data
The number of times each feature was selected with FCBF in the optimization set. (XLSX)
Data
Actual AHI from PSG, values of all the extracted features from the SpO2 signal (ODI3, statistical moments, PSD, and DWT features), and the classification scores of LR, SVM, and MLP of each subject in the cross-validation set. (XLSX)
Article
Full-text available
FULL-TEXT VIEW-ONLY VERSION of the paper: http://rdcu.be/HbJ1 Purpose: A variety of statistical models based on overnight oximetry has been proposed to simplify the detection of children with suspected obstructive sleep apnea syndrome (OSAS). Despite the usefulness reported, additional thorough comparative analyses are required. This study was ai...
Conference Paper
Este estudio se centra en la caracterización del síndrome de la apnea-hipopnea del sueño (SAHS) infantil en el EEG nocturno. Para ello, se ha realizado un análisis espectral sobre los registros de 294 sujetos pediátricos (5-9 años) seleccionados en escuelas infantiles. El análisis espectral derivó en la definición de dos nuevas bandas de interés: i...
Conference Paper
Background: Increasing accessibility to diagnostic resources would enable early detection of obstructive sleep apnea syndrome (OSAS) in children. Portable oximetry and automated signal processing techniques could speed up diagnosis. Aims and objectives: To assess symbolic dynamics as a reliable technique to characterize complex fluctuations of por...
Article
Objective: To evaluate whether detrended fluctuation analysis (DFA) provides information that improves the diagnostic ability of the oximetry signal in the diagnosis of paediatric sleep apnoea-hypopnoea syndrome (SAHS). Approach: A database composed of 981 blood oxygen saturation (SpO2) recordings in children was used to extract DFA-derived feat...
Article
Objective: This study is aimed at assessing symbolic dynamics as a reliable technique to characterise complex fluctuations of portable oximetry in the context of automated detection of childhood obstructive sleep apnoea-hypopnoea syndrome (OSAHS). Approach: Nocturnal oximetry signals from 142 children with suspected OSAHS were acquired using the...
Conference Paper
Pediatric sleep apnea-hypopnea syndrome (SAHS) is a highly prevalent respiratory disorder that may impose many negative effects on the health and development of children. Due to the drawbacks of overnight polysomnography (PSG), the gold standard diagnosis technique, automated analysis of nocturnal oximetry has emerged as a simplified alternative. I...
Conference Paper
This study aims at assessing the bispectral analysis of blood oxygen saturation (SpO2) from nocturnal oximetry to help in pediatric sleep apnea-hypopnea syndrome (SAHS) diagnosis. Recent studies have found excessive redundancy in the SAHS-related information usually extracted from SpO2, while proposing only two features as a reduced set to be used....
Article
Overnight oximetry has been proposed as an accessible, simple, and reliable technique for obstructive sleep apnea syndrome (OSAS) diagnosis. From visual inspection to advanced signal processing, several studies demonstrated the usefulness of oximetry as screening tool. Technical advances increased the diagnostic ability of oximetry. Currently, high...
Article
Full-text available
Background and objective: The aim of this study was to assess the utility of bispectrum-based oximetry approaches as a complementary tool to traditional techniques in the screening of pediatric sleep apnea-hypopnea syndrome (SAHS). Methods: 298 blood oxygen saturation (SpO2) signals from children ranging 0-13 years of age were recorded during ov...
Article
Background: The vast majority of children around the world undergoing adenotonsillectomy for obstructive sleep apnea-hypopnea syndrome (OSA) are not objectively diagnosed with nocturnal polysomnography (NPSG) due to access availability and cost issues. Automated analysis of nocturnal oximetry (nSpO2), which is readily and globally available, could...
Article
Full-text available
Background The coexistence of obstructive sleep apnea syndrome (OSAS) and chronic obstructive pulmonary disease (COPD) leads to increased morbidity and mortality. The development of home-based screening tests is essential to expedite diagnosis. Nevertheless, there is still very limited evidence on the effectiveness of portable monitoring to diagnos...
Data
Actual AHI from PSG, ODI3, ODI4, and estimated AHI from the proposed oximetry-based MLP ANN both in the hospital and at home of each subject in the non-COPD test dataset. (XLSX)
Data
Actual AHI from PSG, ODI3, ODI4, and estimated AHI from the proposed oximetry-based MLP ANN both in the hospital and at home of each subject in the COPD test dataset. (XLSX)
Article
Full-text available
The aim of this paper is to evaluate the evolution of irregularity and variability of airflow (AF) signals as sleep apnoea-hypopnoea syndrome (SAHS) severity increases in children. We analyzed 501 AF recordings from children 6.2 ± 3.4 years old. The respiratory rate variability (RRV) signal, which is obtained from AF, was also estimated. The propos...
Article
This paper presents an electroencephalographic (EEG) P300-based brain-computer interface (BCI) Internet browser. The system uses the “odd-ball” row-col paradigm for generating the P300 evoked potentials on the scalp of the user, which are immediately processed and translated into web browser commands. There were previous approaches for controlling...
Conference Paper
In the sleep apnea-hypopnea syndrome (SAHS) context, airflow signal plays a key role for the simplification of the diagnostic process. It is measured during the standard diagnostic test by the acquisition of two simultaneous sensors: a nasal prong pressure (NPP) and a thermistor (TH). The current study focuses on the comparison of their spectral co...
Conference Paper
Sleep apnea hypopnea syndrome (SAHS) is a highly prevalent respiratory disorder that may cause many negative consequences for the health and development of children. The gold standard for diagnosis is the overnight polysomnography (PSG), which is a high cost, complex, intrusive, and time-demanding technique. To improve the early detection of pediat...