Applying Cross Approximate Entropy to Blood Oxygen Saturation and Heart Rate from Nocturnal Oximetry in Screening for Obstructive Sleep Apnea
Daniel Álvarez (University of Valladolid, Spain), Roberto Hornero (University of Valladolid, Spain), María García (University of Valladolid, Spain), Félix del Campo (Hospital Universitario del Rio Hortega of Valladolid, Spain) and Miguel López (University of Valladolid, Spain)
Copyright: © 2008
Obstructive sleep apnea (OSA) syndrome is a major sleep-related breathing disorder, affecting 1% to 5% of adult men in western countries (Young, Peppard, & Gottlieb, 2002). This disease is now the most common respiratory referral to many sleep units (Douglas 2002). OSA syndrome is associated with excessive daytime sleepiness, neurocognitive deficits, and psychological problems. A significant number of patients with suspicion of OSA present mild to severe symptoms of depression (Schwartz, Kohler, & Karatinos, 2005). OSA syndrome is also a risk factor for cardiovascular disease morbidity and mortality (Leung and Bradley 2001). People with OSA have higher risk of sudden death due to cardiac causes during sleep than the general population (Gami, Howard, Olson, & Somers, 2005). Furthermore, subjects with OSA present an increased risk of being involved in traffic and work accidents (Barbé, Pericas, Muñoz, Findley, Anto, & Agustí, 1998).
Key Terms in this Chapter
Hypopnea Event: The partial reduction of respiratory flow for at least 10 seconds accompanied by a 4% or more decrease in the saturation of hemoglobin.
Apnea Event: The omplete cessation of airflow for at least 10 seconds.
Heart Rate (HR): The frequency of the cardiac cycle equal to the number of contractions of the heart (heart beats) in 1 minute commonly expressed as beats per minute (bpm).
Cross Approximate Entropy (Cross-ApEn): The nonlinear measure of asynchrony between two paired time series.
Polysomnography (PSG): A multiparametric test used in the study of sleep and breathing usually performed during the night in a specialized sleep unit. PSG records biophysiological and neurophysiological data, including electroencephalogram (EEG), electrocardiogram (ECG), electrooculogram (EOG), electromiogram (EMG), measurement of chest wall movement and airflow, and oximetry.
Blood Oxygen Saturation (SaO2): A percentage of hemoglobin binding sites in the bloodstream occupied by oxygen.
Oximetry: The noninvasive indirect measure of the percentage of arterial oxygen combined with the hemoglobin blood oxygen saturation (SaO2), usually accompanied by an estimation of the heart rate (HR).
Obstructive Sleep Apnea (OSA) Syndrome: A sleep disorder characterized by repetitive obstruction of the upper airway despite the presence of respiratory effort, resulting in oxygen desaturations and arousals during sleep.
Nonlinear System: A system whose behavior is not subject to the principle of superposition, that is, its behavior is not expressible as the sum of its parts.