{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,25]],"date-time":"2026-03-25T11:31:27Z","timestamp":1774438287502,"version":"3.50.1"},"reference-count":33,"publisher":"MDPI AG","issue":"11","license":[{"start":{"date-parts":[[2017,11,16]],"date-time":"2017-11-16T00:00:00Z","timestamp":1510790400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>The object of the proposed paper is to design and analyze the performance of a non-contact heart rate variability (HRV) measuring device based on ultrasound transducers. The rationale behind non-contact HRV measurement is the goal of obtaining a means of long term monitoring of a patient\u2019s heart performance. Due to its complexity as a non-contact measuring device, influential physical quantities, error source and other perturbations were thoroughly investigated. For medical purposes it is of utmost importance to define the target uncertainty of a measuring method from the side of physicians, while it is the role of scientists to realistically evaluate all uncertainty contributions. Within this paper we present a novelty method of non-contact HRV measurement based on ultrasound transducers operating at two frequencies simultaneously. We report laboratory results and clinical evaluations are given for healthy subjects as well as patients with known heart conditions. Furthermore, laboratory tests were conducted on subjects during a relaxation period, and after 1 min physical activity<\/jats:p>","DOI":"10.3390\/s17112637","type":"journal-article","created":{"date-parts":[[2017,11,16]],"date-time":"2017-11-16T11:10:02Z","timestamp":1510830602000},"page":"2637","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":19,"title":["Design and Clinical Evaluation of a Non-Contact Heart Rate Variability Measuring Device"],"prefix":"10.3390","volume":"17","author":[{"given":"Jure","family":"Kranjec","sequence":"first","affiliation":[{"name":"Faculty of Electrical Engineering, University of Ljubljana, Tr\u017ea\u0161ka 25, 1000 Ljubljana, Slovenia"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Samo","family":"Begu\u0161","sequence":"additional","affiliation":[{"name":"Faculty of Electrical Engineering, University of Ljubljana, Tr\u017ea\u0161ka 25, 1000 Ljubljana, Slovenia"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1161-9197","authenticated-orcid":false,"given":"Gregor","family":"Ger\u0161ak","sequence":"additional","affiliation":[{"name":"Faculty of Electrical Engineering, University of Ljubljana, Tr\u017ea\u0161ka 25, 1000 Ljubljana, Slovenia"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Matja\u017e","family":"\u0160inkovec","sequence":"additional","affiliation":[{"name":"Clinical Department of Cardiology, University Medical Centre Ljubljana, Zalo\u0161ka 7, 1000 Ljubljana, Slovenia"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Janko","family":"Drnov\u0161ek","sequence":"additional","affiliation":[{"name":"Faculty of Electrical Engineering, University of Ljubljana, Tr\u017ea\u0161ka 25, 1000 Ljubljana, Slovenia"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Domen","family":"Hudoklin","sequence":"additional","affiliation":[{"name":"Faculty of Electrical Engineering, University of Ljubljana, Tr\u017ea\u0161ka 25, 1000 Ljubljana, Slovenia"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2017,11,16]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"1043","DOI":"10.1161\/01.CIR.93.5.1043","article-title":"Heart rate variability: standards of measurement, physiological interpretation and clinical use. Task Force of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology","volume":"93","author":"Camm","year":"1996","journal-title":"Circulation"},{"key":"ref_2","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_3","first-page":"514","article-title":"Heart rate variability: A noninvasive electrocardiographic method to measure the autonomic nervous system","volume":"134","author":"Sztajzel","year":"2004","journal-title":"Swiss Med. Wkly."},{"key":"ref_4","first-page":"12466","article-title":"A Review Paper on Analysis of Electrocardiograph (ECG) Signal for the Detection of Arrhythmia Abnormalities","volume":"3","author":"Joshi","year":"2014","journal-title":"Int. J. Adv. Res. Electr. Electron. Instrum. Eng."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"141","DOI":"10.1016\/S1569-9048(03)00090-9","article-title":"Finger plethysmography\u2014A method for monitoring finger blood flow during sleep disordered breathing","volume":"136","author":"Grote","year":"2003","journal-title":"Respir. Physiol. Neurobiol."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"119","DOI":"10.1007\/s10558-009-9082-3","article-title":"Limitations of Oximetry to Measure Heart Rate Variability Measures","volume":"9","author":"Lu","year":"2009","journal-title":"Cardiovasc. Eng."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"102","DOI":"10.1016\/j.bspc.2014.03.004","article-title":"Non-contact heart rate and heart rate variability measurements: A review","volume":"13","author":"Kranjec","year":"2014","journal-title":"Biomed. Signal Process. Control"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"485","DOI":"10.1007\/s11517-012-1021-6","article-title":"A comprehensive survey of wearable and wireless ECG monitoring systems for older adults","volume":"51","author":"Baig","year":"2013","journal-title":"Med. Boil. Eng. Comput."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"106","DOI":"10.1109\/RBME.2010.2084078","article-title":"Dry-Contact and Noncontact Biopotential Electrodes: Methodological Review","volume":"3","author":"Chi","year":"2010","journal-title":"IEEE Rev. Biomed. Eng."},{"key":"ref_10","unstructured":"(2017, October 12). Available online: https:\/\/www.biopac.com\/wp-content\/uploads\/app109.pdf."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"889","DOI":"10.2165\/00007256-200333120-00003","article-title":"Heart rate variability in athletes","volume":"33","author":"Aubert","year":"2003","journal-title":"Sports Med."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"138","DOI":"10.1016\/S1566-0702(01)00284-3","article-title":"Wavelet decomposition analysis of heart rate variability in aerobic athletes","volume":"90","author":"Verlinde","year":"2001","journal-title":"Auton. Neurosci."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"773","DOI":"10.1007\/s40279-013-0071-8","article-title":"Training Adaptation and Heart Rate Variability in Elite Endurance Athletes: Opening the Door to Effective Monitoring","volume":"43","author":"Plews","year":"2013","journal-title":"Sports Med."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"307","DOI":"10.1016\/j.ijcard.2017.05.001","article-title":"Heart rate variability to monitor performance in elite athletes: Criticalities and avoidable pitfalls","volume":"240","author":"Lucini","year":"2017","journal-title":"Int. J. Cardiol."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"23","DOI":"10.1016\/j.apergo.2008.01.019","article-title":"Autonomic nervous system and subjective ratings of strain in air-traffic control","volume":"40","author":"Collet","year":"2009","journal-title":"Appl. Ergonom."},{"key":"ref_16","first-page":"89","article-title":"Detection of drivers drowsiness by means of HRV analysis","volume":"38","author":"Vicente","year":"2011","journal-title":"Proc. Comput. Cardiol."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"7235","DOI":"10.1016\/j.eswa.2010.12.028","article-title":"Applying neural network analysis on heart rate variability data to assess driver fatigue","volume":"38","author":"Patel","year":"2011","journal-title":"Expert Syst. Appl."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"351","DOI":"10.1109\/TNSRE.2010.2047656","article-title":"Psychophysiological responses to robotic rehabilitation tasks in stroke","volume":"18","author":"Novak","year":"2010","journal-title":"IEEE Trans. Neural Syst. Rehabil. Eng."},{"key":"ref_19","first-page":"21","article-title":"Improvement in Heart Rate Variability during Mild Cognitive Task Following Concussion","volume":"2","author":"Ferraro","year":"2017","journal-title":"Int. J. Exerc. Sci."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"271","DOI":"10.1007\/s40501-017-0118-9","article-title":"Heart Rate Variability Responses to a Standardized Virtual Reality Exposure in Veterans with PTSD","volume":"4","author":"Ridout","year":"2017","journal-title":"Curr. Treat. Options Psychiatry"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"838","DOI":"10.1109\/TIM.2013.2287118","article-title":"Novel Methods for Noncontact Heart Rate Measurement: A Feasibility Study","volume":"63","author":"Kranjec","year":"2014","journal-title":"IEEE Trans. Instrum. Meas."},{"key":"ref_22","doi-asserted-by":"crossref","unstructured":"Wei, B., He, X., Zhang, C., and Wu, X. (2017). Non-contact, synchronous dynamic measurement of respiratori rate and heart rate based on dual sensitive regions. Biomed. Eng. Online, 16.","DOI":"10.1186\/s12938-016-0300-0"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"56","DOI":"10.1016\/j.infrared.2017.05.010","article-title":"Resting heart rate estimation using PIR sensors","volume":"85","author":"Kapu","year":"2017","journal-title":"Infrared Phys. Technol."},{"key":"ref_24","doi-asserted-by":"crossref","unstructured":"Blackford, E.B., Piasecki, A.M., and Estepp, J.R. (2016). Measuring pulse rate variability using long-range, non-contact imaging photoplethysmography. Eng. Med. Biol. Soc.","DOI":"10.1117\/12.2208130"},{"key":"ref_25","unstructured":"(2017, October 12). Available online: https:\/\/www.biopac.com\/product-category\/research\/systems\/mp150-starter-systems\/."},{"key":"ref_26","unstructured":"(2017, October 12). Available online: https:\/\/www.biopac.com\/product\/ecg-electrocardiogram-amplifier\/."},{"key":"ref_27","unstructured":"(2017, October 12). Available online: https:\/\/www.biopac.com\/wp-content\/uploads\/ECG100C.pdf."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"192","DOI":"10.1002\/mop.24877","article-title":"Multitunable microwave system for touchless heartbeat detection and heart rate variability extraction","volume":"52","author":"Obeid","year":"2010","journal-title":"Microw. Opt. Technol. Lett."},{"key":"ref_29","unstructured":"(2017, October 12). Air Ultrasonic Ceramic Transducers. Available online: http:\/\/www.prowave.com.tw\/english\/products\/ut\/ep\/40pt16.htm."},{"key":"ref_30","unstructured":"(2017, October 12). Standing Waves. Available online: https:\/\/isaacphysics.org\/concepts\/cp_standing_waves."},{"key":"ref_31","unstructured":"Smith, S.W. (1970, January 01). Audio Processing. Available online: http:\/\/www.dspguide.com\/ch22\/1.htm."},{"key":"ref_32","first-page":"969","article-title":"Interim Guidelines on limits of human exposure to airborne ultrasound. International Non-Ionizing Radiation Committee of the International Radiation Protection Association","volume":"46","author":"Jammet","year":"1984","journal-title":"Health Phys."},{"key":"ref_33","first-page":"253","article-title":"A review of current ultrasound exposure limits","volume":"21","author":"Howaard","year":"2005","journal-title":"J. Occup. Health Saf."}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/17\/11\/2637\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T18:49:45Z","timestamp":1760208585000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/17\/11\/2637"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2017,11,16]]},"references-count":33,"journal-issue":{"issue":"11","published-online":{"date-parts":[[2017,11]]}},"alternative-id":["s17112637"],"URL":"https:\/\/doi.org\/10.3390\/s17112637","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2017,11,16]]}}}