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Validation of a new device for photoplethysmographic measurement of multi-site arterial pulse wave velocity

Sondej Tadeusz, Jannasz Iwona, Sieczkowski Krzysztof, Dobrowolski Andrzej, Obiała Karolina, Targowski Tomasz, Olszewski Robert

Biocybernetics and Biomedical Engineering

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2021

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Vol. 41, no. 4

1664--1684

EN

Pulse wave velocity (PWV) is commonly used for assessing arterial stiffness and it is a useful and accurate cardiovascular mortality predictor. Currently, many techniques and devices for PWV measurement are known, but they are usually expensive and require operator experience. One possible solution for PWV measurement is photoplethysmography (PPG), which is convenient, inexpensive and provides continuous PWV results. The aim of this paper is validation of a new device for PPG sensor-based measurement of multisite arterial PWV using a SphygmoCor XCEL (as the reference device) according to the recommendations of the Artery Society Guidelines (ASG). In this study, 108 subjects (56 men and 52 women, 20–91 years in 3 required age groups) were enrolled. The multi-site PWV was simultaneous measured by 7 PPG sensors commonly used in pulse oximetry in clinical settings. These sensors were placed on the forehead, and right and left earlobes, fingers and toes. Pulse transit time (PTT) was measured offline as the difference of time delay between two onsets of the pulse wave determined by the intersecting tangent method. The PWV was calculated by dividing the distance between PPG sensors by PTT. During PPG signals measurement, reference carotid to femoral PWV (cfPWV) was performed with a SphygmoCor XCEL system. The Pearson correlation coefficient (r) between the obtained PWV results was calculated. The Bland-Altman method was used to establish the level of agreement between the two devices. Mean difference (md) and standard deviation (SD) were also calculated. The multi-site PWV was highly correlated with accuracy at the ASG-defined level of ‘‘Acceptable” (md < 1.0 m/s and SD ≤ 1.5 m/s) with cfPWV: forehead - right toe (r = 0.75, md = 0.20, SD = 0.97), forehead - left toe (r = 0.79, md = 0.18, SD = 0.91), right ear - right toe (r = 0.79, md = 0.11, SD = 0.96), left ear - left toe (r = 0.75, md = 0.43, SD = 0.99), right ear - left toe (r = 0.78, md = 0.40, SD = 0.93), left ear - right toe (r = 0.78, md = 0.11, SD = 0.96), right finger - right toe (r = 0.66, md = 0.95, SD = 1.29), left finger - lefttoe (r = 0.67, md = 0.68, SD = 1.35). This study showed that PWV measured with the multisite PPG system, in relation to the obtained numerical values, correlated very well with that measured using the commonly known applanation tonometry method. However, it should be noted, that the measured PWV concerns the central and muscular part of the arterial tree while the cfPWV is only for the central one. The best results were obtained when the proximal PPG sensor was placed on the head (ear or forehead) and the distal PPG sensor on the toe. PPG sensors can be placed in many sites at the same time, which provides greater freedom of their configuration. Multi-site photoplethysmography is an alternative method for PWV measurement and creates new possibilities for the diagnostics of cardiovascular diseases.

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Ocena sztywności tętnic na podstawie analizy falkowej sygnału fotopletyzmograficznego

Wilk B., Marek W.

Pomiary Automatyka Kontrola

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2013

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R. 59, nr 12

1301--1303

PL

W artykule opisano wirtualny przyrząd opracowany do oceny sztywności ścian dużych tętnic na podstawie analizy sygnału PPG reprezentującego falę tętna obwodowego. Na podstawie lokalizacji charakterystycznych punktów fali tętna są wyznaczane wartości parametrów stosowanych do oceny sztywności tętnic: CT, PPT, RI, SI, IWD. Do detekcji wcięcia dykrotycznego wykorzystano rozwinięcie falkowe uzyskane za pomocą CWT. Trend sygnału PPG wydzielono na podstawie dekompozycji sygnału wg algorytmu Mallata.

EN

Arterial stiffness is recognized as a major determinant of cardiovascular risk. The arterial pressure waveform contains valuable information indicative of both aortic and systemic arterial stiffness. This paper describes a virtual instrument for assessment of arterial stiffness by analyzing the peripheral pulse waveform. The developed software (in LabVIEW) consists of a program for data acquisition and a program for peripheral pulse wave analysis. To record a peripheral pulse wave at a finger, a transmission-type photoplethysmographic (PPG) sensor was used. The PPG sensor is sensitive to variations in the blood volume. The PPG signal was amplified, acquired using a data acquisition system, and stored. Digital signal processing was then performed. Firstly, a non-linear trend and noise were removed from the PPG signal using the DWT (Fig. 1). Then the characteristic points of the pulse wave were detected using a peak detector (Fig. 2). For identification of an invisible dicrotic notch the CWT was successfully employed (Fig. 4). All the detected peaks were verified using the refractory period as a criterion for false detection. Based on the location of the characteristic points of the pulse wave, several parameters including CT, PPT, SI, RI, IWD were calculated to quantify the arterial stiffness (Tab. 1). This study proposes a simple and effective non-invasive method for assessing arterial stiffness to identify individuals with cardiovascular risk earlier and treat them preventively.

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Ocena sztywności tętnic na podstawie analizy kształtu fali tętna obwodowego

Wilk B.

Pomiary Automatyka Kontrola

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2009

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R. 55, nr 12

1001-1003

PL

W artykule przedstawiono metodę oceny sztywności naczyń tętniczych na podstawie analizy sygnału fotopletyzmograficznego (tzw. PPG) reprezentującego falę tętna obwodowego. Do rejestracji fali tętna zastosowano czujnik fotopletyzmograficzny (wariant prześwietleniowy) umieszczony na palcu. W pracy opisano algorytm opracowany do przetwarzania sygnału PPG, który umożliwia wyznaczenie parametrów przydatnych do oceny sztywności ścian tętnic. Omówiono także problemy detekcji charakterystycznych punktów fali tętna.

EN

Arterial stiffness is a well-known risk factor of cardiovascular dise-ase and a predictor of cardiovascular events. Recent studies have shown that the arterial pulse waveform provides a great deal of information on arterial stiffness. Vascular stiffness plays an important role in controlling the speed of aortic wave propagation. In young healthy subjects, the central aortic wave generated by left ventricular ejection is reflected from the periphery in diastole maintaining a normal coronary flow rate. When the wall stiffness of large arteries increases, the reflected wave appears earlier in the aorta, raising central aortic pressure during systole. In this paper the method for estimating arterial stiffness from the peripheral pulse waveform is described. Peripheral pulse waveforms were recorded at the finger using a transmission-type, photoplethysmographic sensor. Pho-toplethysmo-graphy is a non-invasive optical technique sensitive to variations in blood volume and perfusion in the tissue. Fig.1 shows a typical peripheral volume pulse wave shape represented by the AC component of the photoplethysmographic signal (the so-called PPG signal). The purpose of this study was to develop a simple and effective method for analysis of the PPG signal later used for extracting features for assessment of the arterial stiffness. The following parameters widely used to quantify the arterial stiffness were calculated (see Tab. 1): the crest time, the reflection index (RI), and the time between the systolic and diastolic peaks (related to the transit time of the pressure waves from the root of the aorta to the site of reflection and back). The crest time and the reflection index (RI) are related to the pulse wave velocity in large arteries. In this paper some problems of detection of the characteristic points from the PPG signal are also discussed.