{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,19]],"date-time":"2026-02-19T16:34:05Z","timestamp":1771518845429,"version":"3.50.1"},"reference-count":64,"publisher":"MDPI AG","issue":"8","license":[{"start":{"date-parts":[[2021,8,6]],"date-time":"2021-08-06T00:00:00Z","timestamp":1628208000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100008530","name":"European Regional Development Fund","doi-asserted-by":"publisher","award":["DPI2017-84280-R"],"award-info":[{"award-number":["DPI2017-84280-R"]}],"id":[{"id":"10.13039\/501100008530","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100008530","name":"European Regional Development Fund","doi-asserted-by":"publisher","award":["RTC-2017-6516-1"],"award-info":[{"award-number":["RTC-2017-6516-1"]}],"id":[{"id":"10.13039\/501100008530","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/100014440","name":"Ministerio de Ciencia, Innovaci\u00f3n y Universidades","doi-asserted-by":"publisher","award":["PRE2018-085219"],"award-info":[{"award-number":["PRE2018-085219"]}],"id":[{"id":"10.13039\/100014440","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100004837","name":"Ministerio de Ciencia e Innovaci\u00f3n","doi-asserted-by":"publisher","award":["RYC2019-028566-I"],"award-info":[{"award-number":["RYC2019-028566-I"]}],"id":[{"id":"10.13039\/501100004837","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/100000002","name":"National Institutes of Health","doi-asserted-by":"publisher","award":["HL130984"],"award-info":[{"award-number":["HL130984"]}],"id":[{"id":"10.13039\/100000002","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/100000002","name":"National Institutes of Health","doi-asserted-by":"publisher","award":["HL140548"],"award-info":[{"award-number":["HL140548"]}],"id":[{"id":"10.13039\/100000002","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/100000002","name":"National Institutes of Health","doi-asserted-by":"publisher","award":["AG061824"],"award-info":[{"award-number":["AG061824"]}],"id":[{"id":"10.13039\/100000002","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Entropy"],"abstract":"<jats:p>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 OSA. Here, this work aimed to assess HRV using bispectral analysis in children with OSA for signal characterization and diagnostic purposes in two large pediatric databases (0\u201313 years). The first database (training set) was composed of 981 overnight ECG recordings obtained during polysomnography. The second database (test set) was a subset of the Childhood Adenotonsillectomy Trial database (757 children). We characterized three bispectral regions based on the classic HRV frequency ranges (very low frequency: 0\u20130.04 Hz; low frequency: 0.04\u20130.15 Hz; and high frequency: 0.15\u20130.40 Hz), as well as three OSA-specific frequency ranges obtained in recent studies (BW1: 0.001\u20130.005 Hz; BW2: 0.028\u20130.074 Hz; BWRes: a subject-adaptive respiratory region). In each region, up to 14 bispectral features were computed. The fast correlation-based filter was applied to the features obtained from the classic and OSA-specific regions, showing complementary information regarding OSA alterations in HRV. This information was then used to train multi-layer perceptron (MLP) neural networks aimed at automatically detecting pediatric OSA using three clinically defined severity classifiers. Both classic and OSA-specific MLP models showed high and similar accuracy (Acc) and areas under the receiver operating characteristic curve (AUCs) for moderate (classic regions: Acc = 81.0%, AUC = 0.774; OSA-specific regions: Acc = 81.0%, AUC = 0.791) and severe (classic regions: Acc = 91.7%, AUC = 0.847; OSA-specific regions: Acc = 89.3%, AUC = 0.841) OSA levels. Thus, the current findings highlight the usefulness of bispectral analysis on HRV to characterize and diagnose pediatric OSA.<\/jats:p>","DOI":"10.3390\/e23081016","type":"journal-article","created":{"date-parts":[[2021,8,8]],"date-time":"2021-08-08T21:49:41Z","timestamp":1628459381000},"page":"1016","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":21,"title":["Bispectral Analysis of Heart Rate Variability to Characterize and Help Diagnose Pediatric Sleep Apnea"],"prefix":"10.3390","volume":"23","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-8628-4563","authenticated-orcid":false,"given":"Adri\u00e1n","family":"Mart\u00edn-Montero","sequence":"first","affiliation":[{"name":"Biomedical Engineering Group, University of Valladolid, 47002 Valladolid, Spain"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1237-3424","authenticated-orcid":false,"given":"Gonzalo C.","family":"Guti\u00e9rrez-Tobal","sequence":"additional","affiliation":[{"name":"Biomedical Engineering Group, University of Valladolid, 47002 Valladolid, Spain"},{"name":"CIBER-BBN, Centro de Investigaci\u00f3n Biom\u00e9dica en Red en Bioingenier\u00eda, Biomateriales y Nanomedicina, 28029 Madrid, Spain"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8195-6036","authenticated-orcid":false,"given":"David","family":"Gozal","sequence":"additional","affiliation":[{"name":"Department of Child Health and the Child Health Research Institute, The University of Missouri School of Medicine, Columbia, MO 65212, USA"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5648-206X","authenticated-orcid":false,"given":"Ver\u00f3nica","family":"Barroso-Garc\u00eda","sequence":"additional","affiliation":[{"name":"Biomedical Engineering Group, University of Valladolid, 47002 Valladolid, Spain"},{"name":"CIBER-BBN, Centro de Investigaci\u00f3n Biom\u00e9dica en Red en Bioingenier\u00eda, Biomateriales y Nanomedicina, 28029 Madrid, Spain"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1027-2395","authenticated-orcid":false,"given":"Daniel","family":"\u00c1lvarez","sequence":"additional","affiliation":[{"name":"Biomedical Engineering Group, University of Valladolid, 47002 Valladolid, Spain"},{"name":"CIBER-BBN, Centro de Investigaci\u00f3n Biom\u00e9dica en Red en Bioingenier\u00eda, Biomateriales y Nanomedicina, 28029 Madrid, Spain"}]},{"given":"F\u00e9lix","family":"del Campo","sequence":"additional","affiliation":[{"name":"Biomedical Engineering Group, University of Valladolid, 47002 Valladolid, Spain"},{"name":"CIBER-BBN, Centro de Investigaci\u00f3n Biom\u00e9dica en Red en Bioingenier\u00eda, Biomateriales y Nanomedicina, 28029 Madrid, Spain"},{"name":"Sleep-Ventilation Unit, Pneumology Service, R\u00edo Hortega University Hospital, 47012 Valladolid, Spain"}]},{"given":"Leila","family":"Kheirandish-Gozal","sequence":"additional","affiliation":[{"name":"Department of Child Health and the Child Health Research Institute, The University of Missouri School of Medicine, Columbia, MO 65212, USA"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9915-2570","authenticated-orcid":false,"given":"Roberto","family":"Hornero","sequence":"additional","affiliation":[{"name":"Biomedical Engineering Group, University of Valladolid, 47002 Valladolid, Spain"},{"name":"CIBER-BBN, Centro de Investigaci\u00f3n Biom\u00e9dica en Red en Bioingenier\u00eda, Biomateriales y Nanomedicina, 28029 Madrid, Spain"}]}],"member":"1968","published-online":{"date-parts":[[2021,8,6]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"704","DOI":"10.1542\/peds.109.4.704","article-title":"Clinical practice guideline: Diagnosis and management of childhood","volume":"109","author":"Marcus","year":"2002","journal-title":"Pediatrics"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"866","DOI":"10.1164\/ajrccm.153.2.8564147","article-title":"Standards and indications for cardiopulmonary sleep studies in children","volume":"153","author":"Society","year":"1996","journal-title":"Am. J. Respir. Crit. Care Med."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"425","DOI":"10.1586\/ers.11.7","article-title":"Obstructive sleep apnea syndrome in children","volume":"5","author":"Tauman","year":"2011","journal-title":"Expert Rev. Respir. Med."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"616","DOI":"10.1542\/peds.102.3.616","article-title":"Sleep-Disordered Breathing and School Performance in Children","volume":"102","author":"Gozal","year":"1998","journal-title":"Pediatrics"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"739","DOI":"10.1164\/rccm.201510-2099OC","article-title":"Effect of sleep-disordered breathing severity on cognitive performance measures in a large community cohort of young school-aged children","volume":"194","author":"Hunter","year":"2016","journal-title":"Am. J. Respir. Crit. Care Med."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"1561","DOI":"10.1378\/chest.123.5.1561","article-title":"BP and Arterial Distensibility in Children With Primary Snoring","volume":"123","author":"Kwok","year":"2003","journal-title":"Chest"},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"1394","DOI":"10.1542\/peds.107.6.1394","article-title":"Snoring During Early Childhood and Academic Performance at Ages Thirteen to Fourteen Years","volume":"107","author":"Gozal","year":"2001","journal-title":"Pediatrics"},{"key":"ref_8","unstructured":"Iber, C., Ancoli-Israel, S., Chesson, A.L., and Quan, S.F. (2007). The AASM Manual for the Scoring of Sleep and Associated Events: Rules, Terminology and Technical Specifications, American Academy Sleep Medicine. [1st ed.]."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"e714","DOI":"10.1542\/peds.2012-1672","article-title":"Diagnosis and management of childhood obstructive sleep apnea syndrome","volume":"130","author":"Marcus","year":"2012","journal-title":"Pediatrics"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"597","DOI":"10.5664\/jcsm.2172","article-title":"Rules for Scoring Respiratory Events in Sleep: Update of the 2007 AASM Manual for the Scoring of Sleep and Associated Events","volume":"08","author":"Berry","year":"2012","journal-title":"J. Clin. Sleep Med."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"255","DOI":"10.5665\/sleep.3392","article-title":"Overnight polysomnography versus respiratory polygraphy in the diagnosis of pediatric obstructive sleep apnea","volume":"37","author":"Tan","year":"2014","journal-title":"Sleep"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"1020","DOI":"10.1378\/chest.14-1959","article-title":"Reliability of Home Respiratory Polygraphy for the Diagnosis of Sleep Apnea in Children","volume":"147","author":"Gozal","year":"2015","journal-title":"Chest"},{"key":"ref_13","doi-asserted-by":"crossref","unstructured":"Chiner, E., C\u00e1novas, C., Molina, V., Sancho-Chust, J.N., Va\u00f1es, S., Pastor, E., and Martinez-Garcia, M.A. (2020). Home Respiratory Polygraphy is Useful in the Diagnosis of Childhood Obstructive Sleep Apnea Syndrome. J. Clin. Med., 9.","DOI":"10.3390\/jcm9072067"},{"key":"ref_14","doi-asserted-by":"crossref","unstructured":"Guti\u00e9rrez-Tobal, G.C., \u00c1lvarez, D., Kheirandish-Gozal, L., Campo, F., Gozal, D., and Hornero, R. (2021). Reliability of machine learning to diagnose pediatric obstructive sleep apnea: Systematic review and meta-analysis. Pediatr. Pulmonol., 25423.","DOI":"10.1002\/ppul.25423"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"75","DOI":"10.1016\/j.smrv.2012.04.004","article-title":"Does treatment of SDB in children improve cardiovascular outcome?","volume":"17","author":"Vlahandonis","year":"2013","journal-title":"Sleep Med. Rev."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"58","DOI":"10.1016\/j.sleep.2017.09.012","article-title":"The impact of sleep disordered breathing on cardiovascular health in overweight children","volume":"41","author":"Horne","year":"2018","journal-title":"Sleep Med."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"551","DOI":"10.1016\/j.clinph.2015.05.025","article-title":"Autonomic imbalance during apneic episodes in pediatric obstructive sleep apnea","volume":"127","author":"Vitelli","year":"2016","journal-title":"Clin. Neurophysiol."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"354","DOI":"10.1093\/oxfordjournals.eurheartj.a014868","article-title":"Heart rate variability. Standards of measurement, physiological interpretation, and clinical use","volume":"17","author":"Malik","year":"1996","journal-title":"Eur. Heart J."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"1031","DOI":"10.1007\/s11517-006-0119-0","article-title":"Heart rate variability: A review","volume":"44","author":"Acharya","year":"2006","journal-title":"Med. Biol. Eng. Comput."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"126","DOI":"10.1016\/S0140-6736(84)90062-X","article-title":"Cyclical Variation of the Heart Rate in Sleep Apnoea Syndrome","volume":"323","author":"Guilleminault","year":"1984","journal-title":"Lancet"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"1143","DOI":"10.1109\/TBME.2003.817636","article-title":"Comparison of Detrended fluctuation Analysis and Spectral Analysis of Heart Rate Variability in Sleep and Sleep Apnea","volume":"50","author":"Penzel","year":"2003","journal-title":"IEEE Trans. Biomed. Eng."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"358","DOI":"10.1111\/j.1365-2869.2009.00807.x","article-title":"Sleep-disordered breathing in children is associated with impairment of sleep stage-specific shift of cardiac autonomic modulation","volume":"19","author":"Liao","year":"2010","journal-title":"J. Sleep Res."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"605","DOI":"10.1007\/s11325-012-0727-x","article-title":"Autonomic dysfunction in children with sleep disordered breathing","volume":"17","author":"Walter","year":"2013","journal-title":"Sleep Breath."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"784","DOI":"10.1093\/sleep\/27.4.784","article-title":"Detection of Obstructive Sleep Apnea in Pediatric Subjects using Surface Lead Electrocardiogram Features","volume":"27","author":"Shouldice","year":"2004","journal-title":"Sleep"},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"205","DOI":"10.1002\/ppul.21268","article-title":"Heart Rate Variability in Childhood Obstructive Sleep Apnea","volume":"46","author":"Kwok","year":"2011","journal-title":"Pediatr. Pulmonol."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"1005","DOI":"10.1109\/TBME.2008.2009340","article-title":"Discrimination of sleep-apnea-related decreases in the amplitude fluctuations of ppg signal in children by HRV analysis","volume":"56","author":"Gil","year":"2009","journal-title":"IEEE Trans. Biomed. Eng."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"1771","DOI":"10.1038\/s41390-020-01138-2","article-title":"Heart rate variability spectrum characteristics in children with sleep apnea","volume":"89","author":"Gozal","year":"2021","journal-title":"Pediatr. Res."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"345","DOI":"10.1007\/BF02318382","article-title":"Autonomic cardiovascular control in children with obstructive sleep apnea","volume":"9","author":"Baharav","year":"1999","journal-title":"Clin. Auton. Res."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"679","DOI":"10.1016\/j.medengphy.2010.04.009","article-title":"Application of higher order statistics\/spectra in biomedical signals-A review","volume":"32","author":"Chua","year":"2010","journal-title":"Med. Eng. Phys."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"1963","DOI":"10.1088\/0967-3334\/36\/9\/1963","article-title":"Obstructive sleep apnea detection using spectrum and bispectrum analysis of single-lead ECG signal","volume":"36","author":"Atri","year":"2015","journal-title":"Physiol. Meas."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"71","DOI":"10.3389\/fphys.2015.00071","article-title":"Complexity analyses show two distinct types of nonlinear dynamics in short heart period variability recordings","volume":"6","author":"Porta","year":"2015","journal-title":"Front. Physiol."},{"key":"ref_32","doi-asserted-by":"crossref","unstructured":"Mart\u00edn-Gonz\u00e1lez, S., Navarro-Mesa, J.L., Juli\u00e1-Serd\u00e1, G., Ram\u00edrez-\u00c1vila, G.M., and Ravelo-Garc\u00eda, A.G. (2018). Improving the understanding of sleep apnea characterization using Recurrence Quantification Analysis by defining overall acceptable values for the dimensionality of the system, the delay, and the distance threshold. PLoS ONE, 13.","DOI":"10.1371\/journal.pone.0194462"},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"151","DOI":"10.1093\/sleep\/20.2.151","article-title":"Heart Rate Variability in Children With Obstructive Sleep Apnea","volume":"20","author":"Aljadeff","year":"1997","journal-title":"Sleep"},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"145","DOI":"10.1080\/03091900601050862","article-title":"Cardiac state diagnosis using higher order spectra of heart rate variability","volume":"32","author":"Chua","year":"2008","journal-title":"J. Med. Eng. Technol."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"1","DOI":"10.2174\/1874431100903010001","article-title":"Cardiac Health Diagnosis Using Higher Order Spectra and Support Vector Machine","volume":"3","author":"Chua","year":"2009","journal-title":"Open Med. Inform. J."},{"key":"ref_36","unstructured":"Saliu, S., Birand, A., and Kudaiberdieva, G. (2002, January 3\u20136). Bispectral analysis of heart rate variability signal. Proceedings of the 11th European Signal Processing Conference, Toulouse, France."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"816","DOI":"10.1016\/j.compbiomed.2012.06.005","article-title":"Bispectral analysis and genetic algorithm for congestive heart failure recognition based on heart rate variability","volume":"42","author":"Yu","year":"2012","journal-title":"Comput. Biol. Med."},{"key":"ref_38","first-page":"781","article-title":"Instantaneous bispectral analysis of heartbeat dynamics for the assessment of major depression","volume":"Volume 42","author":"Garcia","year":"2016","journal-title":"Proceedings of the 2015 Computing in Cardiology Conference (CinC)"},{"key":"ref_39","doi-asserted-by":"crossref","unstructured":"Shao, S., Wang, T., Song, C., Chen, X., Cui, E., and Zhao, H. (2019). Obstructive Sleep Apnea Recognition Based on Multi-Bands Spectral Entropy Analysis of Short-Time Heart Rate Variability. Entropy, 21.","DOI":"10.3390\/e21080812"},{"key":"ref_40","doi-asserted-by":"crossref","unstructured":"Zheng, L., Pan, W., Li, Y., Luo, D., Wang, Q., and Liu, G. (2017). Use of Mutual Information and Transfer Entropy to Assess Interaction between Parasympathetic and Sympathetic Activities of Nervous System from HRV. Entropy, 19.","DOI":"10.3390\/e19090489"},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"503","DOI":"10.1016\/j.sleep.2011.10.035","article-title":"HHT based cardiopulmonary coupling analysis for sleep apnea detection","volume":"13","author":"Liu","year":"2012","journal-title":"Sleep Med."},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"1591","DOI":"10.1164\/rccm.201705-0930OC","article-title":"Nocturnal oximetry-based evaluation of habitually snoring children","volume":"196","author":"Hornero","year":"2017","journal-title":"Am. J. Respir. Crit. Care Med."},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"1509","DOI":"10.5665\/sleep.1388","article-title":"The Childhood Adenotonsillectomy Trial (CHAT): Rationale, Design, and Challenges of a Randomized Controlled Trial Evaluating a Standard Surgical Procedure in a Pediatric Population","volume":"34","author":"Redline","year":"2011","journal-title":"Sleep"},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"2366","DOI":"10.1056\/NEJMoa1215881","article-title":"A randomized trial of adenotonsillectomy for childhood sleep apnea","volume":"368","author":"Marcus","year":"2013","journal-title":"N. Engl. J. Med."},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"105083","DOI":"10.1016\/j.cmpb.2019.105083","article-title":"Usefulness of recurrence plots from airflow recordings to aid in paediatric sleep apnoea diagnosis","volume":"183","author":"Gozal","year":"2020","journal-title":"Comput. Methods Programs Biomed."},{"key":"ref_46","doi-asserted-by":"crossref","first-page":"104167","DOI":"10.1016\/j.compbiomed.2020.104167","article-title":"Bispectral analysis of overnight airflow to improve the pediatric sleep apnea diagnosis","volume":"129","author":"Gozal","year":"2021","journal-title":"Comput. Biol. Med."},{"key":"ref_47","doi-asserted-by":"crossref","unstructured":"Barroso-Garc\u00eda, V., Guti\u00e9rrez-Tobal, G.C., Kheirandish-Gozal, L., \u00c1lvarez, D., Vaquerizo-Villar, F., Crespo, A., del Campo, F., Gozal, D., and Hornero, R. (2017). Irregularity and variability analysis of airflow recordings to facilitate the diagnosis of paediatric sleep apnoea-hypopnoea syndrome. Entropy, 19.","DOI":"10.3390\/e19090447"},{"key":"ref_48","doi-asserted-by":"crossref","first-page":"399","DOI":"10.1016\/S0010-4825(01)00009-9","article-title":"The use of the Hilbert transform in ECG signal analysis","volume":"31","author":"Benitez","year":"2001","journal-title":"Comput. Biol. Med."},{"key":"ref_49","doi-asserted-by":"crossref","first-page":"123","DOI":"10.3390\/e17010123","article-title":"Assessment of time and frequency domain entropies to detect sleep apnoea in heart rate variability recordings from men and women","volume":"17","author":"Hornero","year":"2015","journal-title":"Entropy"},{"key":"ref_50","first-page":"1205","article-title":"Efficient Feature Selection via Analysis of Relevance and Redundancy","volume":"5","author":"Yu","year":"2004","journal-title":"J. Mach. Learn. Res."},{"key":"ref_51","doi-asserted-by":"crossref","first-page":"141","DOI":"10.1016\/j.cmpb.2017.12.020","article-title":"Utility of bispectrum in the screening of pediatric sleep apnea-hypopnea syndrome using oximetry recordings","volume":"156","author":"Crespo","year":"2018","journal-title":"Comput. Methods Programs Biomed."},{"key":"ref_52","first-page":"1157","article-title":"An introduction to variable and feature selection","volume":"3","author":"Guyon","year":"2003","journal-title":"J. Mach. Learn. Res."},{"key":"ref_53","doi-asserted-by":"crossref","unstructured":"Bishop, C. (1995). Neural Networks for Pattern Recognition, Oxford University Press.","DOI":"10.1093\/oso\/9780198538493.001.0001"},{"key":"ref_54","doi-asserted-by":"crossref","first-page":"013110","DOI":"10.1063\/1.4906038","article-title":"Multiple feature extraction and classification of electroencephalograph signal for Alzheimers\u2019 with spectrum and bispectrum","volume":"25","author":"Wang","year":"2015","journal-title":"Chaos Interdiscip. J. Nonlinear Sci."},{"key":"ref_55","doi-asserted-by":"crossref","first-page":"1079","DOI":"10.1109\/TBME.2009.2037734","article-title":"PTT variability for discrimination of sleep apnea related decreases in the amplitude fluctuations of PPG signal in children","volume":"57","author":"Gil","year":"2010","journal-title":"IEEE Trans. Biomed. Eng."},{"key":"ref_56","doi-asserted-by":"crossref","first-page":"240","DOI":"10.1109\/JBHI.2013.2267096","article-title":"Pulse rate variability analysis for discrimination of sleep-apnea-related decreases in the amplitude fluctuations of pulse photoplethysmographic signal in children","volume":"18","author":"Gil","year":"2014","journal-title":"IEEE J. Biomed. Health Inform."},{"key":"ref_57","doi-asserted-by":"crossref","first-page":"118","DOI":"10.1016\/j.compbiomed.2015.05.007","article-title":"Automated detection of sleep apnea in infants: A multi-modal approach","volume":"63","author":"Cohen","year":"2015","journal-title":"Comput. Biol. Med."},{"key":"ref_58","doi-asserted-by":"crossref","unstructured":"Vaquerizo-Villar, F., Alvarez, D., Kheirandish-Gozal, L., Gutierrez-Tobal, G.C., Barroso-Garcia, V., Santamaria-Vazquez, E., Del Campo, F., Gozal, D., and Hornero, R. (2021). A convolutional neural network architecture to enhance oximetry ability to diagnose pediatric obstructive sleep apnea. IEEE J. Biomed. Health Inform., Early Access.","DOI":"10.1109\/JBHI.2020.3048901"},{"key":"ref_59","first-page":"1863","article-title":"Noninvasive Cardiorespiratory Signals Analysis for Asthma Evolution Monitoring in Preschool Children","volume":"67","author":"Milagro","year":"2019","journal-title":"IEEE Trans. Biomed. Eng."},{"key":"ref_60","doi-asserted-by":"crossref","first-page":"1332","DOI":"10.1109\/JBHI.2017.2775059","article-title":"Nocturnal Heart Rate Variability Spectrum Characterization in Preschool Children with Asthmatic Symptoms","volume":"22","author":"Milagro","year":"2018","journal-title":"IEEE J. Biomed. Heal. Inform."},{"key":"ref_61","doi-asserted-by":"crossref","first-page":"282","DOI":"10.1109\/JPROC.2015.2476824","article-title":"Wiener\u2013Granger Causality in Network Physiology With Applications to Cardiovascular Control and Neuroscience","volume":"104","author":"Porta","year":"2016","journal-title":"Proc. IEEE"},{"key":"ref_62","doi-asserted-by":"crossref","first-page":"1512","DOI":"10.1109\/TBME.2007.913418","article-title":"Statistical Approach to Quantify the Presence of Phase Coupling Using the Bispectrum","volume":"55","author":"Siu","year":"2008","journal-title":"IEEE Trans. Biomed. Eng."},{"key":"ref_63","doi-asserted-by":"crossref","first-page":"77","DOI":"10.1016\/0167-2789(92)90102-S","article-title":"Testing for nonlinearity in time series: The method of surrogate data","volume":"58","author":"Theiler","year":"1992","journal-title":"Phys. D Nonlinear Phenom."},{"key":"ref_64","doi-asserted-by":"crossref","first-page":"1067","DOI":"10.1088\/0967-3334\/28\/9\/008","article-title":"Assessing nonlinear properties of heart rate variability from short-term recordings: Are these measurements reliable?","volume":"28","author":"Maestri","year":"2007","journal-title":"Physiol. Meas."}],"container-title":["Entropy"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1099-4300\/23\/8\/1016\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T06:41:48Z","timestamp":1760164908000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1099-4300\/23\/8\/1016"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2021,8,6]]},"references-count":64,"journal-issue":{"issue":"8","published-online":{"date-parts":[[2021,8]]}},"alternative-id":["e23081016"],"URL":"https:\/\/doi.org\/10.3390\/e23081016","relation":{},"ISSN":["1099-4300"],"issn-type":[{"value":"1099-4300","type":"electronic"}],"subject":[],"published":{"date-parts":[[2021,8,6]]}}}