Digital processing of ECG and PPG signals for study of arterial parameters for cardiovascular risk assessment

One of the biggest single cause of mortality in the world is cardiovascular disease (CVD) and hence it is recognized that an early detection of its onset is vital for effective preventive therapies. Aortic stiffness has been shown to be an independent predictor of CVD, but its measurement is complex and time consuming. An alternative much simpler way of doing it is by looking for arterial properties such as arterial stiffness. This paper presents methods of estimating arterial parameters from measured ECG and PPG signals. PPG signal can be acquired easily by measuring the transmission of infra-red light through the finger tip. Two methods of obtaining arterial parameters have been used, one using simultaneously acquired ECG and PPG signals and another using PPG signal only. Pulse wave velocity, which is an indicator of arterial stiffness, has been measured using pulse wave transmit time derived from simultaneously recorded ECG and PPG signals. Arterial parameters like stiffness index, augmentation index etc have been derived from the PPG signals. These parameters have been obtained for subjects in two age groups and it is observed that the parameters show clear changes for the two age groups thus demonstrating their efficacy in detecting changes in the arteries with age. Power spectral analysis has been performed to show how frequency spectra are different for the two age groups. This study demonstrates the usefulness of ECG and PPG analysis in investigating the changes in the arterial characteristics of the vascular system with age; it has potential applications in healthcare.