Sleep-wake stages classification using heart rate signals from pulse oximetry

The most important index of obstructive sleep apnea/hypopnea syndrome (OSAHS) is the apnea/hyponea index (AHI). The AHI is the number of apnea/hypopnea events per hour of sleep. Algorithms for the screening of OSAHS from pulse oximetry estimate an approximation to AHI counting the desaturation events without consider the sleep stage of the patient. This paper presents an automatic system to determine if a patient is awake or asleep using heart rate (HR) signals provided by pulse oximetry. In this study, 70 features are estimated using entropy and complexity measures, frequency domain and time-scale domain methods, and classical statistics. The dimension of feature space is reduced from 70 to 40 using three different schemes based on forward feature selection with support vector machine and feature importance with random forest. The algorithms were designed, trained and tested with 5000 patients from the Sleep Heart Health Study database. In the test stage, 10-fold cross validation method was applied obtaining performances up to 85.2% accuracy, 88.3% specificity, 79.0% sensitivity, 67.0% positive predictive value, and 91.3% negative predictive value. The results are encouraging, showing the possibility of using HR signals obtained from the same oximeter to determine the sleep stage of the patient, and thus potentially improving the estimation of AHI based on only pulse oximetry.Fil: Casal, Ramiro. Universidad Nacional de Entre Ríos. Instituto de Investigación y Desarrollo en Bioingeniería y Bioinformática - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigación y Desarrollo en Bioingeniería y Bioinformática; ArgentinaFil: Di Persia, Leandro Ezequiel. Universidad Nacional del Litoral. Facultad de Ingeniería y Ciencias Hídricas. Departamento de Informática. Laboratorio de Investigaciones en Señales e Inteligencia Computacional; ArgentinaFil: Schlotthauer, Gaston. Universidad Nacional de Entre Ríos. Instituto de Investigación y Desarrollo en Bioingeniería y Bioinformática - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigación y Desarrollo en Bioingeniería y Bioinformática; Argentin

Automatic analysis of overnight airflow to help in the diagnosis of pediatric obstructive sleep apnea

La apnea obstructiva del sueño (AOS) pediátrica es una enfermedad respiratoria altamente prevalente e infradiagnosticada que puede afectar negativamente a las funciones fisiológicas y cognitivas de los niños, causándoles graves deficiencias neurocognitivas, cardiometabólicas y endocrinas. El método estándar para su diagnóstico es la polisomnografía nocturna, una prueba compleja, de elevado coste, altamente intrusiva y poco accesible, lo que genera largas listas de espera y retrasos en el diagnóstico. Por ello, es necesario desarrollar pruebas diagnósticas más sencillas. Una de estas alternativas es el análisis automático de señales cardiorrespiratorias. Así, esta tesis doctoral presenta un compendio de cuatro publicaciones que proponen el uso de novedosos métodos de procesado de señal (no lineal, espectral, bispectral, gráficos de recurrencia y wavelet) que permiten caracterizar exhaustivamente el comportamiento del flujo aéreo nocturno de los niños y simplificar el diagnóstico de la apnea obstructiva del sueño pediátrica.Departamento de Teoría de la Señal y Comunicaciones e Ingeniería TelemáticaDoctorado en Tecnologías de la Información y las Telecomunicacione

The Role of Surface Tension of Upper Airway Lining Liquid and Breathing Route in Sleep Disordered Breathing

This thesis examines the relationship between surface tension in the upper airway liquid, breathing route, and sleep disordered breathing. Upper airway surface tension values were examined in both healthy subjects and in those with obstructive sleep apnoea. To determine whether the enforced oral breathing route induced sleep disordered breathing via surface tension mediated mechanisms, healthy subjects were given exogenous surfactant with enforced oral route of breathing during sleep. The relationship between uncontrolled route of breathing and surface tension was then examined in subjects with severe obstructive sleep apnoea. Finally, exogenous surfactant and normal saline were administered to subjects to determine the presence of any therapeutic effect on obstructive sleep apnoea. The studies in this thesis i) described a range of surface tensions in healthy subjects, and in those with OSA, ii) investigated the role of breathing route on upper airway surface tension and OSA severity, and iii) investigated the role of exogenous surfactant as a therapeutic agent in both oral breathing induced sleep disordered breathing (in healthy subjects) and in subjects with mild to moderate obstructive sleep apnoea

Diseño y evaluación de metodologías de análisis automático de la oximetría nocturna como método simplificado de detección del síndrome de apnea-hipopnea obstructiva del sueño en niños. Validación en el hospital y en el domicilio.

El síndrome de apnea-hipopnea obstructiva del sueño (SAHOS) es una enfermedad de alta prevalencia en la población infantil, con una importante morbilidad y elevado impacto sociosanitario, en la que la detección precoz es esencial para iniciar un adecuado tratamiento, el cual debe ser siempre individualizado. El SAHOS es una alteración fisiopatológica compleja y multifactorial, en la que no sólo influye una susceptibilidad genética e individual (factores anatómicos y dinámicos), sino también de estilo de vida. Los factores de riesgo más frecuentes son la hipertrofia adenoamigdalar y la obesidad. Los síntomas en los niños son escasos, son principalmente nocturnos y requieren un alto nivel de sospecha. El SAHOS no diagnosticado o no tratado se relaciona con diferentes consecuencias metabólicas, cardiovasculares, neurocognitivas, inflamatorias, conductuales y falta de desarrollo estaturoponderal, lo que conduce a un empeoramiento del estado de salud en términos generales y disminución de calidad de vida.Departamento de Anatomía y RadiologíaDoctorado en Investigación en Ciencias de la Salu

An integrated understanding of the effects of sleep disordered breathing on the physiology of the developing child

The role of Sleep Disordered Breathing (SDB) in adult hypertension and cardiovascular morbidity is well established and increased blood pressure and cardiac remodeling has been demonstrated in children with severe SDB. There is less evidence suggesting that milder forms of SDB are associated with cardiovascular anomalies. Therefore this thesis contains a series of studies which compares the underlying physiology, particularly vascular function in children with mild SDB with aged matched healthy non-snoring children. Children with SDB were recruited at the Women’s and Children’s Hospital, through the Ear, Nose and Throat surgical waitlist, prior to treatment to resolve their SDB. All children underwent an overnight sleep study to assess their SDB severity for each study. Chapter 1 is a literature review which provides a brief summary of the autonomic nervous system and the physiology of sleep. A synopsis of the disorder is also presented including information on diagnosis and treatment of the disorder. An in depth assessment of the literature pertaining specifically to studies measuring cardiovascular, autonomic and inflammatory response in children with SDB is summarized and the physiological pathways that lead to hypertension are explained. Chapter 2 assesses Flow Mediated Dilatation, a validated measure of endothelial function in healthy children ranging from 6 – 16 years. At the time of publication there were no studies using FMD in children as young as 6 years. This study shows a positive relationship between the time to reach maximal dilation after ischemia in the brachial artery and both age and body habitus. Younger children reached maximal dilation by 35s while older children reached maximal dilation by 60s+. This paper is important as it helped to determine the age range and analysis for the following study. Chapter 3 outlines the results of a study in young children with primary snoring aged 5-9 years using FMD. We showed that both resting and hyperaemic velocity time integral (VTi; area under the curve of velocity over ejection time) was significantly higher in children referred for evaluation of SDB (n=23) compared with healthy matched controls (n=11). Other groups report similar results in blood flow velocity measured in middle cerebral arteries using transcranial Doppler in children with primary snoring. We also found that the brachial artery took approximately 20 seconds longer to fully dilate after induced hyperaemia in the children with SDB compared with controls. Of note is that both children with SDB and controls in our FMD study demonstrated similar rates of dilatation in the initial 30s, suggesting that endothelial function is preserved, but after 30s the groups diverged and children with SDB took longer to reach maximum dilatation. The time delay in maximum dilatation suggests augmented cell-to-cell connectivity as the dilatation process moves from the endothelial cells through smooth muscle, ending in the adventitial layer. Having defined vascular changes in medium sized vessels, in Chapter 3, Chapter 4 investigates the vascular effects of SDB on the heart and major vessels using cardiac MRI in children aged 5-14 years including primary snorers/mild SDB and non-snoring controls. This study found a significant increase in peak systolic blood flow velocity in the ascending aorta in children with SDB (n = 12) compared to controls (n = 7). The increase in blood flow velocity was similar to increases reported by other groups (20-30%) in cerebral blood flow and by our own group (Chapter 3). A blood sample was also analysed from the children in this study. We used Flow Cytometry to measure cytokine expression of markers of inflammation - Tumor Necrosis Factor alpha (TNFα) and interferon gamma (IFNγ) which are known indicators of cardiovascular disease. We found that there was a significantly higher level of CD8 + cells expressing both TNFα and IFNγ. Consistent with the paradigm that cardiovascular changes are coupled with an increased inflammatory state, we also found a strong positive association between these immune-markers and peak blood flow velocity in the ascending aorta and CD8 + cells expressing IFNγ and TNFα. Our findings support the interrelationship between mild SDB, abnormal vascular function and increased inflammation. While increased inflammatory pathways have been reported in children with severe OSA, this is the first time it has been shown in children diagnosed as primary snorers/mild SDB. Chapter 5 details the relationship between vascular changes observed in Chapter 3 (increased blood flow velocity and time to maximal dilatation in the brachial artery) in relation to autonomic function. We measured sympathetic overactivity using digital pupillometry, and found that it was closely associated with the haemodynamic changes we observed on FMD evaluation of the brachial artery of children with mild SDB. We further undertook the novel step of examining the effect of sympathetic overactivity on the arterial wall by studying the dorsal lingual artery of children undergoing adenotonsillectomy, the accepted treatment for SDB. We found that sympathetic nerve fibre density of the vessel (measured by immunohistochemistry) strongly correlated with the degree of sympathetic overactivity on pupillometric testing and the functional measure from the FMD. To our knowledge this is the first time that functional vascular changes have been correlated to vascular histology in humans. We also explored the association between the sympathetic nerve fibre density brachial artery blood flow velocity and FMD parameters, pupillometry and platelet aggregation (using whole blood samples). Platelet aggregation is a measure of endothelial integrity. Our results show that the children with increased brachial artery blood flow velocity also exhibited increased platelet aggregation in response to the collagen antigen, suggesting endothelial damage. Sympathetic nerve fibre density was also positively associated with increased platelet aggregation, in particular with the aggregation velocity. In addition, there was strong association between the pupillary light reflex variables and the platelet aggregation. Chapter 6 is an overall discussion that amalgamates the findings of each chapter and provides recommendation for future work and consideration.Thesis (Ph.D.) (Research by Publication) -- University of Adelaide, Adelaide Medical School, 201

Thermal imaging developments for respiratory airflow measurement to diagnose apnoea

Sleep-disordered breathing is a sleep disorder that manifests itself as intermittent pauses (apnoeas) in breathing during sleep. The condition disturbs the sleep and can results in a variety of health problems. Its diagnosis is complex and involves multiple sensors attached to the person to measure electroencephalogram (EEG), electrocardiogram (ECG), blood oxygen saturation (pulse oximetry, S

Breathing Rate Estimation From the Electrocardiogram and Photoplethysmogram: A Review.

Breathing rate (BR) is a key physiological parameter used in a range of clinical settings. Despite its diagnostic and prognostic value, it is still widely measured by counting breaths manually. A plethora of algorithms have been proposed to estimate BR from the electrocardiogram (ECG) and pulse oximetry (photoplethysmogram, PPG) signals. These BR algorithms provide opportunity for automated, electronic, and unobtrusive measurement of BR in both healthcare and fitness monitoring. This paper presents a review of the literature on BR estimation from the ECG and PPG. First, the structure of BR algorithms and the mathematical techniques used at each stage are described. Second, the experimental methodologies that have been used to assess the performance of BR algorithms are reviewed, and a methodological framework for the assessment of BR algorithms is presented. Third, we outline the most pressing directions for future research, including the steps required to use BR algorithms in wearable sensors, remote video monitoring, and clinical practice