Multiple time and spectral analysis techniques for comparing the PhotoPlethysmography to PiezoelectricPlethysmography with electrocardiography

Abstract

Photoplethysmography (PPG) is an important, non-invasive and widely used circulatory assessment technique. It is commonly used to measure heart rate and arterial oxygen saturation (SPO₂) by measuring the changes occurred in the blood volume and shows many future perspective applications. In this paper, various time and frequency analysis techniques are used to investigate the spectral differences of the signals obtained using the PPG and the piezoelectricplethysmography (PEPG) techniques. The time delay, effect of respiration and motion artifacts have been investigated in time and frequency domain for both; the PPG and PEPG signals. The electrocardiograph (ECG) signal has been used as a reference. The heart-rate has been estimated using both signals; the PPG and PEPG. The hypothesis of this paper is that PPG and PEPG signals features integration can lead to improve the understanding and estimation of the human body's vital signs by including multi-dimensional features. The results show that the PPG signal is the most robust technique in terms of change in frequency and time domains under the same conditions. Additionally, the PPG signal is less sensitive to artifacts compared to the PEPG signal. Such a study opens possibilities to consider the PPG signal for a wide range of biomedical applications especially in wearable biomedical technologies to utilize its non-invasive property.

Keywords: ECG; Frequency domain; PEPG; PPG; Plethysmography; Time domain.