High-fidelity digital recording and playback sphygmomanometry system: device description and proof of concept Jongshill Lee a , Youngjoon Chee b , Inyoung Kim a , Nikos Karpettas c , Anastasios Kollias c , Neil Atkins d , George S. Stergiou c and Eoin O’Brien e Objectives This study describes the development of a new digital sphygmocorder (DS-II), which allows the digital recording and playback of the Korotkoff sounds, together with cuff pressure waveform, and its performance in a pilot validation study. Materials and methods A condenser microphone and stethoscope head detect Korotkoff sounds and an electronic chip, dedicated to audio-signal processing, is used to record high-quality sounds. Systolic and diastolic blood pressure (SBP/DBP) are determined from the recorded signals with an automatic beat detection algorithm that displays the cuff pressure at each beat on the monitor. Recordings of Korotkoff sounds, with the cuff pressure waveforms, and the simultaneous on-site assessments of SBP/DBP were performed during 100 measurements in 10 individuals. The observers reassessed the recorded signals to verify their accuracy and differences were calculated. Results The features of the high-fidelity DS-II, the technical specifications and the assessment procedures utilizing the playback software are described. Interobserver absolute differences (mean ± SD) in measurements were 0.7 ± 1.1/1.3 ± 1.3 mmHg (SBP/DBP) with a mercury sphygmomanometer and 0.3 ± 0.9/0.8 ± 1.2 mmHg with the DS-II. The absolute DS-II mercury sphygmomanometer differences were 1.3 ± 1.9/1.5 ± 1.3 mmHg (SBP/DBP). Conclusion The high-fidelity DS-II device presents satisfactory agreement with simultaneous measurements of blood pressure with a mercury sphygmomanometer. The device will be a valuable methodology for validating new blood pressure measurement technologies and devices. Blood Press Monit 20:266–272 Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved. Blood Pressure Monitoring 2015, 20:266–272 Keywords: blood pressure measurement, device validation, digital recording, Korotkoff sounds, sphygmomanometry a Department of Biomedical Engineering, Hanyang University, Seoul, b Department of Biomedical Engineering, University of Ulsan, Ulsan, Korea, c Hypertension Center, STRIDE-7, Third University Department of Medicine, Sotiria Hospital, Athens, Greece, d Medaval Ltd and e Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Dublin, Ireland Correspondence to Youngjoon Chee, PhD, School of Electrical Engineering, University of Ulsan, 93 Daehak-Ro, Nam-Gu, Ulsan 680 749, Korea Tel: + 82 52 259 1307; fax: + 82 52 259 1306; e-mail: yjchee@ulsan.ac.kr Received 10 November 2014 Revised 25 December 2014 Accepted 27 April 2015 Introduction Despite the development of new technologies for blood pressure (BP) measurement, Korotkoff sounds ausculta- tion remains the gold standard for noninvasive BP mea- surement [1]. However, automatic noninvasive BP devices that use the oscillometric method are now used widely for office measurements and are used exclusively for out-of-office BP measurements, especially since the ban on mercury sphygmomanometers came into force in April 2014 (http://eur-lex.europa.eu/legal-content/EN/TXT/? uri = CELEX:32012R0847). Devices for BP measurement must be validated against an auscultatory reference method before being recommended for clinical use. The 2010 International Protocol of the European Society of Hypertension stipulates that BP-measuring devices be assessed against a mercury sphygmomanometer in a sample of individuals with specified BP levels [2]. The observer measurements must be recorded accurately to the nearest 2 mmHg, which requires training by an expert [2]. To minimize discrepancies between observers and to allow the playback of recorded sounds, Atkins et al. [3] developed the sphygmocorder, which consisted of a sphygmomanometer, a video recorder, a pump and a computerized program to calculate the results. However, this device had limited application because of the num- ber of interconnected components that had to be housed in a specially constructed cabinet. To improve this sys- tem, a digital sphygmocorder (DS) was developed [4], and visual recording and auscultation were later added [5]. Further testing showed that improvements to the sound quality, in particular to ensure sufficient low- frequency sound recording fidelity for consistent dia- stolic blood pressure (DBP) assessment, and to the recording and playback facilities, were needed so as to make the device suitable for use as a control device in validation studies. Modifications and enhancements to Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal's website (www.bpmonitoring.com). 266 Analytical methods and statistical analysis 1359-5237 Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved. DOI: 10.1097/MBP.0000000000000109 Copyright r 2015 Wolters Kluwer Health, Inc. All rights reserved.