Eduardo Gil

University of Zaragoza | UNIZAR · Department of Computing and Systems Engineering

A novel method for tracking the tidal volume (TV) from electrocardiogram (ECG) is presented. The method is based on the amplitude of ECG-derived respiration (EDR) signals. Three different morphology-based EDR signals and three different amplitude estimation methods have been studied, leading to a total of 9 amplitude-EDR (AEDR) signals per ECG chan...

Obstructive sleep apnea (OSA) is a high-prevalence disease in the general population, often underdiagnosed. The gold standard in clinical practice for its diagnosis and severity assessment is the polysomnography, although in-home approaches have been proposed in recent years to overcome its limitations. Today's ubiquitously presence of wearables ma...

Background Obstructive sleep apnea (OSA) is a risk factor for metabolic syndrome (MetS) in adults, but its association in prepubertal children is still questionable due to the relatively limited cardiometabolic data available and the phenotypic heterogeneity. Objective To identify the role of OSA as a potential mediator of MetS in prepubertal chil...

Photoplethysmography is a key sensing technology which is used in wearable devices such as smartwatches and fitness trackers. Currently, photoplethysmography sensors are used to monitor physiological parameters including heart rate and heart rhythm, and to track activities like sleep and exercise. Yet, wearable photoplethysmography has potential to...

- Heart rate variability (HRV) is modulated by sleep stages and apneic events. Previous studies in children compared classical HRV parameters during sleep stages between obstructive sleep apnea (OSA) and controls. However, HRV-based characterization incorporating both sleep stages and apneic events has not been conducted. Furthermore, recently prop...

The multidimensionality of the stress response has shown the complexity of this phenomenon and therefore the impossibility of finding a unique biomarker among the physiological variables related to stress. An experimental study was designed and performed to guarantee the correct synchronous and concurrent measure of psychometric tests, biochemical...

Pulse photoplethysmography (PPG) is a simple and economical technique for obtaining cardiovascular information. In fact, PPG has become a very popular technology among wearable devices. However, the PPG signal is well-known to be very vulnerable to artifacts, and a good quality signal cannot be expected for most of the time in daily life. The perce...

Heart rate variability (HRV) has been studied for decades in clinical environments. Currently, the exponential growth of wearable devices in health monitoring is leading to new challenges that need to be solved. These devices have relatively poor signal quality and are affected by numerous motion artifacts, with data loss being the main stumbling b...

Se propone un nuevo índice para la estratificación de la apnea del sueño. Este índice se basa en la detección de las frecuencias a las que se producen las variaciones cíclicas de la frecuencia cardíaca (CVHR) en los segmentos con respiración anormal. También se propone un detector de CVHR. Cuando se utiliza conjuntamente con este detector, el índic...

The present paper proposes the design of a sleep monitoring platform. It consists of an entire sleep monitoring system based on a smart glove sensor called UpNEA worn during the night for signals acquisition, a mobile application, and a remote server called AeneA for cloud computing. UpNEA acquires a 3-axis accelerometer signal, a photoplethysmogra...

Objectives: an evaluation of Principal Dynamic Mode (PDM) and Orthogonal Subspace Projection (OSP) methods to characterize the Autonomic Nervous System (ANS) response in three different hyperbaric environments was performed. Methods: ECG signals were recorded in two different stages (baseline and immersion) in three different hyperbaric environm...

The present study investigates the differences in autonomic nervous system (ANS) function and stress response between patients with major depressive disorder (MDD) and healthy subjects by measuring changes in ANS biomarkers. ANS-related parameters are derived from various biosignals during a mental stress protocol consisting of a basal, stress, and...

The ideal moment to withdraw respiratory supply of patients under Mechanical Ventilation at Intensive Care Units (ICU), is not easy to be determined for clinicians. Although the Spontaneous Breathing Trial (SBT) provides a measure of the patients’ readiness, there is still around 15–20% of predictive failure rate. This work is a proof of concept fo...

Objective the aim of this study is to evaluate whether noninvasive autonomic activity assessment could represent a potential tool for the stratification of asthmatic subjects based on symptoms control, using only 10-min electrocardiographic and respiratory signals. Methods several heart rate variability (HRV) derived indexes, which are regarded as...

The main aim of this work is to study the effect of the sampling rate of the photoplethysmographic (PPG) signal for pulse rate variability (PRV) analysis in the time and frequency domains, in stationary conditions. Forehead and finger PPG signals were recorded at 1000 Hz during a rest state, with red and infrared wavelengths, simultaneously with th...

Actualmente, la Prueba de Respiración Espontánea (SBT), indica si un paciente está listo para el destete de la ventilación mecánica. Sin embargo, en torno al 20% de los pacientes “preparados” para ser desintubados, realmente no lo estaban. En este trabajo, se ha estudiado la Capacidad del Barorreflejo durante la hora anterior a la SBT, y se ha vist...

The ideal moment to withdraw respiratory supply of patients under Mechanical Ventilation (MV) at Intensive Care Units (ICU), is not easy to be determined for clinicians. Although the Spontaneous Breathing Trial (SBT) provides a measure of the patients’ readiness, there is still around 15-20% of predictive failure rate. This work explores both Heart...

In this work, a detection and classification method for sleep apnea and hypopnea, using photopletysmography (PPG) and peripheral oxygen saturation ( $SpO_2$ ) signals, is proposed. The detector consists of two parts: one that detects reductions in amplitude fluctuation of PPG (DAP) and one that detects oxygen desaturations. To further differentiat...

Objective: In the present study, a photoplethysmographic (PPG) waveform analysis for assessing differences in autonomic reactivity to mental stress between patients with Major Depressive Disorder (MDD) and healthy control (HC) subjects is presented. Methods: PPG recordings of 40 MDD and 40 HC subjects were acquired at basal conditions, during th...

Weaning is the process of withdrawing mechanical ventilation at the Intensive Care Units. The problem is that around 20% of weaned patients were not actually ready for discontinuation. Studies suggest that vagal dysfunc-tion is lower in patients successfully weaned. Therefore, the Baroreflex Sensitivity (BRS) and Heart Rate Variability (HRV) are es...

The main aim of this work is to identify alterations in the morphology of the pulse photoplethysmogram (PPG) signal, due to the exposure of the subjects to a hyperbaric environment. Additionally, their Pulse Rate Variability (PRV) is analysed to characterise the response of their Autonomic Nervous System (ANS). To do that, 28 volunteers are introdu...

A pilot study on tracking changes in tidal volume (TV) using ECG signals acquired by a wearable armband is presented. The wearable armband provides three ECG channels by using three pairs of dry electrodes, resulting in a device that is convenient for long-term daily monitoring. An additional ECG channel was derived by computing the first principal...

A method for deriving respiratory rate from an armband, which records three-channel electrocardiogram (ECG) using three pairs of dry (no hydrogel) electrodes, is presented. The armband device is especially convenient for long-term (months-years) monitoring because it does not use obstructive leads nor hydrogels/adhesives, which cause skin irritatio...

Cardiorespiratory monitoring is crucial for the diagnosis and management of multiple conditions such as stress and sleep disorders. Therefore, the development of ambulatory systems providing continuous, comfortable, and inexpensive means for monitoring represents an important research topic. Several techniques have been proposed in the literature t...

Stress is a healthy natural response to a perceived or actual threat. However, when stress is persistent, it may decrease work productivity, increase the risk of diseases, and affect the quality of life. Stress is reflected in physiological variables, such as heart rate, blood pressure, and pulse wave velocity among others. A photoplethysmogram (PP...

The relationship between cardiac and respiratory autonomic control has been suggested to be altered in several respiratory disorders. However, and despite the increasing prevalence of asthma, there are not studies assessing the cardiorespiratory coupling (CRC) with respect to the asthmatic status. Since altered autonomic control has been suggested...

Objective: Despite its increasing prevalence, diagnosis of asthma in children remains problematic due to their difficulties in producing repeatable spirometric maneuvers. Moreover, low adherence to inhaled corticosteroids (ICS) treatment could result in permanent airway remodeling. The growing interest in a noninvasive and objective way for monito...

Objective: The simple observation of breathing rate (BR) remains the first and often the most sensitive marker of acute respiratory dysfunction. In fact, there are evidences that drastic changes in BR are a predictive indicator of adverse events (i.e. cardiac arrest). The aim of this study is to develop a camera-based technology that may provide n...

Objective: an evaluation of the location of the photoplethysmogram (PPG) sensor for respiratory rate estimation is performed. Approach: finger-PPG, forehead-PPG, and respiratory signal were simultaneously recorded from 35 subjects while breathing spontaneously, and during controlled respiration experiments at a constant rate from 0.1 Hz to 0.6 H...

The main aim of this work is to model the relationships between parameters extracted from the heart rate variability (HRV) signal, which is derived from the electrocardiogram (ECG), at different stages of a simulated immersion in a hyperbaric chamber. The response of the Autonomic Nervous System is known to be affected by changes in atmospheric pre...

The benefits of yoga have been studied in different fields, from chronic health conditions to mental disorders, showing that it can help to improve the overall health. In particular, it has been proven that yoga also improves the autonomic function. Heart rate variability (HRV) at rest is commonly used as a non-invasive measure of autonomic regulat...

The objective of this work is the identification of significant variations of morphological parameters of the photoplethysmographic (PPG) signal when the subjects are exposed to an increase in atmospheric pressure. To achieve this goal, the PPG signal of 26 subjects, exposed to a hyperbaric environment whose pressure increases up to 5 atm, has been...

The high prevalence of sleep apnea syndrome (SAS) and its direct relationship with an augmented risk of cardiovascular disease (CVD) have raised SAS as a primary public health problem. For this reason, extensive research aiming to understand the interaction between both conditions has been conducted. The advances in non-invasive autonomic nervous...

Novel methods for assessing baroreflex sensitivity (BRS) using only pulse photoplethysmography (PPG) signals are presented. Proposed methods were evaluated with a data set containing electrocardiogram (ECG), blood pressure (BP), and PPG signals from 17 healthy subjects during a tilt table test. The methods are based on a surrogate of α index, which...

formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> ${Objective:}$ Electrocardiogram (ECG) has been regarded as a source of respiratory information with the main focus in the estimation of the respiratory rate. Although little research concerning the estimation of tidal volume (TV) has been conducted,...

Objective: The aim of this work is to evaluate and compare five fiducial points for the temporal location of each pulse wave from forehead and finger photoplethysmographic (PPG) pulse wave signals to perform pulse rate variability (PRV) analysis as a surrogate for heart rate variability (HRV) analysis. Approach: Forehead and finger PPG signals w...

Objective: This paper proposes an approach to better estimate the sympathovagal balance (SB) and the respiratory sinus arrhythmia (RSA) after separating respiratory influences from the heart rate (HR). Methods: The separation is performed using orthogonal subspace projections and the approach is first tested using simulated HR and respiratory signa...

Our long-term goal is the development of an automatic identifier of attentional states. In order to accomplish it, we should firstly be able to identify different states based on physiological signals. So, the first aim of this work is to identify the most appropriate features, to detect a subject high performance state. For that, a database of ele...

Social and medical problems associated with stress are increasing globally and seriously affect mental health and wellbeing. However, an effective stress-level monitoring method is still not available. This paper presents a quantitative method for monitoring acute stress levels in healthy young people using biomarkers from physiological signals tha...

A novel technique to derive respiratory rate from pulse photoplethysmographic (PPG) signals is presented. It exploits some morphological features of the PPG pulse that are known to be modulated by respiration: amplitude, slope transit time, and width of the main wave, and time to the first reflected wave. A pulse decomposition analysis technique is...

Objective: In this paper a method for assessment of Quadratic Phase Coupling (QPC) between respiration and Heart Rate Variability (HRV) is presented. Methods: First, a method for QPC detection is proposed named Real Wavelet Biphase (RWB). Then, a method for QPC quantification is proposed based on the Normalized Wavelet Biamplitude (NWB). A simul...

Relationships between inspiration and expiration times, Tin and Tex , and inter-breath interval (BB) were analyzed in a database composed by 120 young healthy volunteers undergoing a session divided in different stages aimed to induce relax and emotional stress, where respiration was recorded with a chest band. Tin and Tex were represented as a fun...

The main aim of this work was to characterise the Autonomic Nervous System (ANS) response in hyperbaric environments using electrocardiogram (ECG) and pulse-photoplethysmogram (PPG) signals. To that end, 26 subjects were introduced into a hyperbaric chamber and five stages with different atmospheric pressures (1 atm; descent to 3 and 5 atm; ascent...

Monitoring of ventricular premature beats (VPBs), being abundant in hemodialysis patients, can provide information on cardiovascular instability and electrolyte imbalance. In this paper, we describe a method for VPB detection which explores the signals acquired from the arterial and the venous pressure sensors, located in the extracorporeal blood c...

Asthma is a chronic lung disease that usually develops during chilhood. Despite that symptoms can almost be controlled with medication, early diagnosis is desirable in order to reduce permanent airway obstruction risk. It has been suggested that abnormal parasympathetic nervous system (PSNS) activity might be closely related with the pathogenesis o...

Finger and forehead pulse photoplethysmographic (PPG) signals are compared as a surrogate for the electrocardiogram (ECG) in Heart Rate Variability (HRV) analysis during tilt table test. PPG signals are usually corrupted by motion artifacts. In this work, robust algorithms for pulse rate estimation have been applied. Classical time and frequency do...

Prophylactic treatment has been proved to reduce hypotension incidence after spinal anesthesia during cesarean labor. However, the use of pharmacological prophylaxis could carry out undesirable side-effects on mother and fetus. Thus, the prediction of hypotension becomes an important challenge. Hypotension events are hypothesized to be related to a...

Asthma is a chronic lung disease that is prone to start during chilhood. Although symptoms can be usually controlled with medication, early diagnosis is crucial to reduce the risk of permanent airway obstruction. Despite the fact that origin of asthma is still uncertain, abnormal parasympathetic nervous system (PNS) activity has been pointed out to...

Early diagnosis of asthma is crucial to avoid long-term effects such as permanent airway obstruction. Pathogenesis of asthma has been related with autonomic nervous system (ANS) dysfunction, concretely with abnormal parasympathetic activity. As heart rate variability (HRV) analysis does reflect ANS activity, it has been employed here in risk of ast...

In this paper a method for the assessment of Quadratic Phase Coupling (QPC) between respiration and Heart Rate Variability is presented and applied to study cardiorespiratory couplings during a tilt table test. Strong QPC related to the dominant respiratory frequency is present and remains unchanged during Autonomic Nervous System changes.

Heart rate variability (HRV) plays an important role in medicine and psychology because it is used to quantify imbalances of the autonomic nervous system (ANS). An important manifestations of the ANS on HRV is also directly related to respiration and it is called respiratory sinus arrhythmia (RSA). This is a controlled phenomenon that leads to a sy...

Hemodialysis patients often suffer from cardiovascular disorders and uremic neuropathy, increasing the propensity to homeostatic imbalance that, in turn, may result in intradialytic complications like cramp, nausea, and, worse, hypotension. Ectopic beats, being abundant in such patients, may lead to imbalance through repeated, sudden drops in blood...

In this work quadratic phase coupling between respiration and heart rate variability (HRV) has been studied during emotional and mental stress using wavelet crossbispectrum (WCB). A total of 80 healthy volunteers subjected to a standard stress protocol have been analyzed. Some features derived from the WCB, such as the frequencies at which the maxi...

Objective: Heart rate turbulence (HRT) has been successfully explored for cardiac risk stratification. While HRT is known to be influenced by the heart rate (HR) and the coupling interval (CI), non-concordant results have been reported on how the CI influences HRT. The purpose of this study is to investigate HRT changes in terms of CI and HR by me...

Respiratory rate and heart rate variability (HRV) are studied as stress markers in a database of young healthy volunteers subjected to acute emotional stress, induced by a modification of the Trier Social Stress Test. First, instantaneous frequency domain HRV parameters are computed using timefrequency analysis in the classical bands. Then, respira...

A method for deriving respiratory rate from smartphone-camera-acquired pulse photoplethysmographic (SCPPG) signal is presented. Our method exploits respiratory information by examining the pulse wave velocity and dispersion from the SCPPG waveform and we term these indices as the pulse width variability (PWV). A method to combine information from s...

Recent clinical and electrophysiological studies reveal a high incidence of autonomic nervous system (ANS) dys-function in patients treated in Intensive Care Units (ICUs). Cognitive rehabilitation (CR) is a behavioral therapy that has proven to be effective improving cognitive deficits in clinical populations with abnormalities in brain activation...

Recent clinical and electrophysiological studies reveal a high incidence of autonomic nervous system (ANS) dysfunction in patients treated in Intensive Care Units (ICUs). Cognitive rehabilitation (CR) is a behavioral therapy that has proven to be effective improving cognitive deficits in clinical populations with abnormalities in brain activation p...

In this work, we analyze changes in respiration during emotional stress induced by a modification of the Trier Social Stress Test. The following stages in the test were analyzed: the pre-relaxing stage, the story telling stage, the anticipation of stress and the video exposition stage. Respiration signal is recorded during the whole test using a th...

Parameters derived from the pulse photoplethysmographic (PPG) signal, such as pulse rate, amplitude, and width variability (PRV, PAV and PWV) have been previously proposed for deriving respiratory rate, obtaining less accurate estimates for higher respiratory rates (0.5-0.6 Hz). In this work we analyze the power of respiration related oscillations...

The risk stratification of sudden cardiac death after my- ocardial infarction plays an important role in cardiology. It influences the treatment of a patient and the use of im- plantable devices. However, the majority of well known methods for stratifying risk still fail to predict sudden car- diac death with high accuracy. The heart rate turbulenc...

A method for estimating respiratory rate from electrocardiogram (ECG) signals is presented. It is based on QRS slopes and R-wave angle, which reflect respiration induced beat morphology variations. The 12 standard leads, 3 leads from vectorcardiogram (VCG), and 2 additional nonstandard leads derived from VCG loops were analyzed. The following serie...

A method for deriving respiratory rate from smartphone-camera-acquired pulse photoplethysmographic (SCPPG) signal is presented. It combines information from three derived respiration signals based on pulse width, amplitude, and rate variability (PWV, PAV, and PRV). Evaluation is performed over a database containing SCPPG signals recorded from 10 he...

A technique for ambulatory diagnosis of the obstructive sleep apnea syndrome (OSAS) in children based on pulse photoplethysmographic (PPG) signal is presented. Decreases in amplitude fluctuations of the PPG signal (DAP) events have been proposed as OSAS discriminator, since they are related to vasoconstriction associated to apnea. Heart rate variab...

A method for respiratory rate estimation from electrocardiogram (ECG), based on variations in QRS complexes slopes, is evaluated over stress testing recordings. Besides the 12 standard, and the 3 vectorcardiogram (VCG), 2 additional leads derived from the VCG are analyzed. A total of 34 slope series were studied, 2 for each lead: slopes between the...

Two cardiovascular parameters of emerging interest suitable for estimation of non-invasive, beat-to-beat, and without cuff, blood pressure parameters are pulse width (PW) and pulse transit time (PTT). In this study the performance of both parameters in estimating beat-to-beat systolic blood pressure (SBP) and diastolic blood pressure (DBP) is analy...