Carotid distension waves acquired with a fiber sensor as an alternative to tonometry for central arterial systolic pressure assessment in young subjects C. Leitão a,⇑ , P. Antunes a , J.L. Pinto a , J.M. Bastos b , P. André c a Instituto de Telecomunicações, I3N and Department of Physics, University of Aveiro, 3810-193 Aveiro, Portugal b Centro Hospitalar do Baixo Vouga E.P.E., Avenida Artur Ravara, 3810-501 Aveiro, Portugal c Instituto de Telecomunicações and Department of Electrical and Computer Engineering, Instituto Superior Técnico, University of Lisbon, 1049-001 Lisboa, Portugal article info Article history: Received 6 July 2016 Received in revised form 11 August 2016 Accepted 20 September 2016 Available online 21 September 2016 Keywords: POF sensor Optical fiber sensor Cardiovascular prevention Arterial pulse waveform Arterial distension waves Central systolic pressure abstract In this work it is evaluated the possibility of central blood pressure assessment using distension waves, obtained with a low cost optical fiber sensor, instead of regular arterial tonometry. Carotid distension and pressure waveforms were acquired in 15 young subjects. Form factors, root-mean-square error (RMSE), harmonic decomposition and central systolic pressures for both techniques were analysed. The pressure waves assessed by the piezoelectric probe had lower form factors than the ones assessed by the optical fiber sensor, due to the different nature of the waves (51.05 ± 5.15% versus 40.53 ± 5.70%), translating in a RMSE of 14 ± 2%. Regarding the harmonic analysis, paired t-tests shown that the first four harmonics are not significant different (p 6 0.05), and Pearson correlation studies retrieve that the 2nd–7th harmonics are correlated (p 6 0.03). Central systolic pressures were also obtained with both techniques displaying a very strong Pearson correlation (0.99) and a small difference of 0.63 ± 2.40 mmHg. These pre-clinical results support a future clinical validation study in larger and broader cohorts. Ó 2016 Elsevier Ltd. All rights reserved. 1. Introduction Arterial brachial blood pressure (BP) and pulse morphology do not invariably reflect central blood pressure values and features [1]. It is now becoming clear that arterial pressure should be eval- uated not only by brachial BP measurements, but also by central BP assessment [2]. Through the proximal arterial tree, in contrary to diastolic (DP) and mean arterial pressure (MAP), pulse pressure is not constant. Systolic pressure (SP) increases towards peripheral arteries [3], inferring that in the brachial artery, which a muscular artery, pulse pressure will generally be higher than in carotid and aortic arteries, both elastic. Pulse waveform measurements are usually performed by arte- rial tonometry with electromechanical probes, such as the case of Complior Analyse Ò (Alam medical) and SphygmoCor Ò (AtCor medi- cal). These pressure probes are pressed to superficial arteries in order to flatten them and sense the pressure changes in its interior [4]. Several studies have also explored the use of distension waves to calculate central pressure parameters [5–7]. In this scope, our team has been working on cost effective tech- niques based on plastic optical fibers (POF) [8,9], aiming the pro- motion of central BP assessment as a primary health care evaluation method. Optical fiber sensors have unique features to fulfill medical instrumentation requirements, such as immunity to electromagnetic radiation and electric insulation from the patient, improving the safety of medical devices and even allowing monitoring physiological signals during magnetic resonance imag- ing [10]. The aims of this study were to evaluate the similarity of disten- sion and pressure pulses of young subjects, and to estimate the car- otid pressure using carotid distension waves assessed with an intensity based optical fiber device, designated as POFpen. The pulse waves were matched in the time and frequency domain with tonometric signals obtained by a standard medical device (Com- plior analyse). Central systolic pressures (cSP) estimated by both technologies were also compared. 2. Material and methods Within this pre-clinical study, 15 subjects were recruited, with ages between 22 and 34 years old, after giving their informed con- sent. In each one, the carotid pulses were acquired with the two http://dx.doi.org/10.1016/j.measurement.2016.09.035 0263-2241/Ó 2016 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. E-mail address: catia.leitao@ua.pt (C. Leitão). Measurement 95 (2017) 45–49 Contents lists available at ScienceDirect Measurement journal homepage: www.elsevier.com/locate/measurement