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The Scientific World Journal
Volume 2013, Article ID 169035, 9 pages
Research Article

New Photoplethysmographic Signal Analysis Algorithm for Arterial Stiffness Estimation

1Department of Biomedical Engineering, Technomedicum, Tallinn University of Technology, Ehitajate tee 5, 19086 Tallinn, Estonia
2Department of Biomedical Engineering, Linköping Univeristy, 581 85 Linköping, Sweden

Received 10 May 2013; Accepted 1 July 2013

Academic Editors: N. Bouguila, M. Engin, and T. Yamasaki

Copyright © 2013 Kristjan Pilt et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


The ability to identify premature arterial stiffening is of considerable value in the prevention of cardiovascular diseases. The “ageing index” (AGI), which is calculated from the second derivative photoplethysmographic (SDPPG) waveform, has been used as one method for arterial stiffness estimation and the evaluation of cardiovascular ageing. In this study, the new SDPPG analysis algorithm is proposed with optimal filtering and signal normalization in time. The filter parameters were optimized in order to achieve the minimal standard deviation of AGI, which gives more effective differentiation between the levels of arterial stiffness. As a result, the optimal low-pass filter edge frequency of 6 Hz and transitionband of 1 Hz were found, which facilitates AGI calculation with a standard deviation of 0.06. The study was carried out on 21 healthy subjects and 20 diabetes patients. The linear relationship between each subject’s age and AGI was found, and a linear model with regression line was constructed. For diabetes patients, the mean AGI value difference from the proposed model was found to be 0.359. The difference was found between healthy and diabetes patients groups with significance level of .