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1 2009

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Ocena sztywności tętnic na podstawie analizy kształtu fali tętna obwodowego

Wilk B.

Pomiary Automatyka Kontrola

2009

R. 55, nr 12

1001-1003

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.

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.