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To achieve this, 28 volunteers were placed in a dry hyperbaric chamber, where they experienced varying pressures from 1 to 5 atmospheres, with five sequential stops lasting five minutes each at different atmospheric pressures. The HRV was dissected into two components: the respiratory component, which is linked to respiration; and the residual component, which is influenced by factors beyond respiration. Nine parameters were assessed, including the respiratory rate, four classic HRV temporal parameters, and four frequency parameters. A k-nearest neighbors classifier based on cosine distance successfully identified the atmospheric pressures to which the subjects were exposed to. The classifier achieved an 88.5% accuracy rate in distinguishing between the 5 atm and 3 atm stages using only four features: respiratory rate, heart rate, and two frequency parameters associated with the subjects\u2019 sympathetic responses. Furthermore, the study identified 6 out of 28 subjects as having atypical responses across all pressure levels when compared to the majority. Interestingly, two of these subjects stood out in terms of gender and having less prior diving experience, but they still exhibited normal responses to immersion. This suggests the potential for establishing distinct safety protocols for divers based on their previous experience and gender.<\/jats:p>","DOI":"10.3390\/s24020447","type":"journal-article","created":{"date-parts":[[2024,1,11]],"date-time":"2024-01-11T05:24:12Z","timestamp":1704950652000},"page":"447","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":3,"title":["Heart Rate Variability to Automatically Identify Hyperbaric States Considering Respiratory Component"],"prefix":"10.3390","volume":"24","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-0690-3193","authenticated-orcid":false,"given":"Mar\u00eda Dolores","family":"Pel\u00e1ez-Coca","sequence":"first","affiliation":[{"name":"Centro Universitario de la Defensa de Zaragoza, 50090 Zaragoza, Spain"},{"name":"BSICoS Group, I3A Institute, University of Zaragoza, IIS Arag\u00f3n, 50009 Zaragoza, Spain"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2596-7237","authenticated-orcid":false,"given":"Alberto","family":"Hernando","sequence":"additional","affiliation":[{"name":"BSICoS Group, I3A Institute, University of Zaragoza, IIS Arag\u00f3n, 50009 Zaragoza, Spain"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0630-4366","authenticated-orcid":false,"given":"Mar\u00eda Teresa","family":"Lozano","sequence":"additional","affiliation":[{"name":"Centro Universitario de la Defensa de Zaragoza, 50090 Zaragoza, Spain"},{"name":"BSICoS Group, I3A Institute, University of Zaragoza, IIS Arag\u00f3n, 50009 Zaragoza, Spain"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4068-127X","authenticated-orcid":false,"given":"Juan","family":"Bolea","sequence":"additional","affiliation":[{"name":"Centro Universitario de la Defensa de Zaragoza, 50090 Zaragoza, Spain"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4746-3139","authenticated-orcid":false,"given":"David","family":"Izquierdo","sequence":"additional","affiliation":[{"name":"GTF Group, I3A Institute, University of Zaragoza, 50009 Zaragoza, Spain"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4273-5403","authenticated-orcid":false,"given":"Carlos","family":"S\u00e1nchez","sequence":"additional","affiliation":[{"name":"BSICoS Group, I3A Institute, University of Zaragoza, IIS Arag\u00f3n, 50009 Zaragoza, Spain"}]}],"member":"1968","published-online":{"date-parts":[[2024,1,11]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"93","DOI":"10.1088\/0967-3334\/19\/1\/008","article-title":"The variability of the photoplethysmographic signal\u2014A potential method for the evaluation of the autonomic nervous system","volume":"19","author":"Nitzan","year":"1998","journal-title":"Physiol. Meas."},{"key":"ref_2","unstructured":"Task Force of the European Society of Cardiology the North American Society of Pacing and Electrophysiology (1996). Heart rate variability standards of measurement, physiological interpretation, and clinical use. Circulation, 93, 1043\u20131065."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"1273","DOI":"10.1109\/TBME.2006.871888","article-title":"A robust method for ECG-based estimation of the respiratory frequency during stress testing","volume":"53","author":"Laguna","year":"2006","journal-title":"IEEE Trans. Biomed. Eng."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"233","DOI":"10.1007\/s11517-012-0954-0","article-title":"Deriving respiration from photoplethysmographic pulse width","volume":"51","author":"Gil","year":"2013","journal-title":"Med. Biol. Eng. 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Health Inform."},{"key":"ref_11","doi-asserted-by":"crossref","unstructured":"Widjaja, D., Caicedo, A., Vlemincx, E., Van Diest, I., and Van Huffel, S. (2014). Separation of respiratory influences from the tachogram: A methodological evaluation. PLoS ONE, 9.","DOI":"10.1371\/journal.pone.0101713"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"61","DOI":"10.7205\/MILMED-D-02-0808","article-title":"Effect of Hyperbaric Pressure During Scuba Diving on Autonomic Modulation of the Cardiac Response: Application of the Continuous Wavelet Transform to the Analysis of Heart Rate Variability","volume":"175","author":"Barbosa","year":"2010","journal-title":"Mil. Med."},{"key":"ref_13","first-page":"29","article-title":"Instantaneous beat-to-beat variability reflects vagal tone during hyperbaric hyperoxia","volume":"30","author":"Lund","year":"2003","journal-title":"Undersea Hyperb. Med."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"39","DOI":"10.1046\/j.1365-201x.2000.00761.x","article-title":"Hyperbaric oxygen increases parasympathetic activity in professional divers","volume":"170","author":"Lund","year":"2000","journal-title":"Acta Physiol. Scand."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"111","DOI":"10.1016\/j.autneu.2010.03.017","article-title":"Effect of cold or thermoneutral water immersion on post-exercise heart rate recovery and heart rate variability indices","volume":"156","author":"Haddad","year":"2010","journal-title":"Auton. Neurosci."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"317","DOI":"10.1007\/s00421-003-0953-9","article-title":"Heart rate variability and autonomic activity at rest and during exercise in various physiological conditions","volume":"90","author":"Perini","year":"2003","journal-title":"Eur. J. Appl. Physiol."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"345","DOI":"10.1007\/s00421-009-1010-0","article-title":"Dominance in cardiac parasympathetic activity during real recreational SCUBA diving","volume":"106","author":"Chouchou","year":"2009","journal-title":"Eur. J. Appl. Physiol."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"174","DOI":"10.1136\/bjsm.35.3.174","article-title":"Effect of immersion, submersion, and scuba diving on heart rate variability","volume":"35","author":"Schipke","year":"2001","journal-title":"Br. J. Sport. Med."},{"key":"ref_19","doi-asserted-by":"crossref","unstructured":"Hernando, A., Posada-Quintero, H., Pel\u00e1ez-Coca, M.D., Gil, E., and Chon, K.H. (2022). Autonomic Nervous System characterization in hyperbaric environments considering respiratory component and non-linear analysis of Heart Rate Variability. Comput. Methods Programs Biomed., 214.","DOI":"10.1016\/j.cmpb.2021.106527"},{"key":"ref_20","doi-asserted-by":"crossref","unstructured":"S\u00e1nchez, C., Hernando, A., Bolea, J., Izquierdo, D., Rodr\u00edguez, G., Olea, A., Lozano, M.T., and Pel\u00e1ez-Coca, M.D. (2023). Enhancing Safety in Hyperbaric Environments through Analysis of Autonomic Nervous System Responses: A Comparison of Dry and Humid Conditions. Sensors, 23.","DOI":"10.3390\/s23115289"},{"key":"ref_21","unstructured":"Bishop, C.M. (2006). Pattern Recognition and Machine Learning, Springer."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"132","DOI":"10.1109\/JBHI.2018.2797982","article-title":"Autonomic Nervous System Measurement in Hyperbaric Environments using ECG and PPG signals","volume":"23","author":"Hernando","year":"2018","journal-title":"IEEE J. Biomed. Health Inform."},{"key":"ref_23","unstructured":"Sokas, D., Gailius, M., and Marozas, V. (2016, January 24). Diver physiology monitor and its graphical user interface. Proceedings of the International Scientific\u2014Practical Conference, Virtual Instruments in Biomedicine, Klaipeda, Lithuania."},{"key":"ref_24","first-page":"2072","article-title":"Electrocardiogram derived respiratory rate from QRS slopes and R-wave angle","volume":"40","author":"Alcaine","year":"2014","journal-title":"Ann. Biomed. Eng."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"204","DOI":"10.1016\/j.jelectrocard.2013.02.014","article-title":"Detection and quantification of acute myocardial ischemia by morphologic evaluation of QRS changes by an angle-based method","volume":"46","author":"Romero","year":"2013","journal-title":"J. Electrocardiol."},{"key":"ref_26","doi-asserted-by":"crossref","unstructured":"S\u00f6rnmo, L., and Laguna, P. (2005). Bioelectrical Signal Processing in Cardiac and Neurological Applications, Academic Press.","DOI":"10.1016\/B978-012437552-9\/50007-6"},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"570","DOI":"10.1109\/TBME.2003.821031","article-title":"A wavelet-based ECG delineator: Evaluation on standard databases","volume":"51","author":"Martinez","year":"2004","journal-title":"IEEE Trans. Biomed. Eng."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"334","DOI":"10.1109\/TBME.2003.808831","article-title":"Analysis of Heart Rate Variability in the Presence of Ectopic Beats Using the Heart Timing Signal","volume":"50","author":"Mateo","year":"2003","journal-title":"IEEE Trans. Biomed. Eng."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"642","DOI":"10.1109\/TBME.2010.2095011","article-title":"The Integral Pulse Frequency Modulation Model with Time-Varying Threshold: Application to Heart Rate Variability Analysis During Exercise Stress Testing","volume":"58","author":"Laouini","year":"2011","journal-title":"Biomed. Eng. IEEE Trans."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"183","DOI":"10.1111\/j.1469-8986.1993.tb01731.x","article-title":"Respiratory sinus arrhythmia: Autonomic origins, physiological mechanisms, and psychophysiological implications","volume":"30","author":"Berntson","year":"1993","journal-title":"Psychophysiology"},{"key":"ref_31","unstructured":"Matlab, M. (2023, November 15). Classification Learner App. Available online: https:\/\/www.mathworks.com\/help\/stats\/classification-learner-app.html."},{"key":"ref_32","doi-asserted-by":"crossref","unstructured":"Forsyth, D. (2019). Applied Machine Learning, Springer.","DOI":"10.1007\/978-3-030-18114-7"},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"67","DOI":"10.1080\/20964471.2019.1586074","article-title":"Discriminating among tectonic settings of spinel based on multiple machine learning algorithms Discriminating among tectonic settings of spinel based on multiple machine learning algorithms","volume":"3","author":"Han","year":"2019","journal-title":"Big Earth Data"},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"122","DOI":"10.1016\/j.cose.2019.01.007","article-title":"DriverAuth: A risk-based multi-modal biometric-based driver authentication scheme for ride-sharing platforms","volume":"83","author":"Gupta","year":"2019","journal-title":"Comput. Secur."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"R103","DOI":"10.1152\/ajpregu.00074.2006","article-title":"Impaired defense of core temperature in aged humans during mild cold stress","volume":"292","author":"DeGroot","year":"2007","journal-title":"Am. J. Physiol. -Regul. Integr. Comp. Physiol."},{"key":"ref_36","unstructured":"Pendergast, D.R., Moon, R.E., Krasney, J.J., Held, H.E., and Zamparo, P. (2015). Comprehensive Physiology, John Wiley & Sons, Ltd."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"6","DOI":"10.1007\/BF02691277","article-title":"Mechanism of the human diving response","volume":"29","author":"Gooden","year":"1994","journal-title":"Integr. Physiol. Behav. Sci."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"589","DOI":"10.22462\/11.12.2017.10","article-title":"Effects of prolonged and repeated immersions on heart rate variability and complexity in military divers","volume":"44","author":"Berry","year":"2017","journal-title":"Undersea Hyperb. Med."},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"1550","DOI":"10.1109\/JBHI.2020.3020743","article-title":"Photoplethysmographic Waveform and Pulse Rate Variability Analysis in Hyperbaric Environments","volume":"25","author":"Hernando","year":"2021","journal-title":"IEEE J. Biomed. Health Inform."}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/24\/2\/447\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T13:44:30Z","timestamp":1760103870000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/24\/2\/447"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2024,1,11]]},"references-count":39,"journal-issue":{"issue":"2","published-online":{"date-parts":[[2024,1]]}},"alternative-id":["s24020447"],"URL":"https:\/\/doi.org\/10.3390\/s24020447","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2024,1,11]]}}}