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Analyzing the Endothelial Function by Means of Photoplethysmogram Signal Modeling

Amiri, Mina | 2012

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 43250 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Zahedi, Edmond; Behnia, Fereidoon
  7. Abstract:
  8. The endothelial (the artery inner lumen cells) function is associated with cardiovascular risk factors. Its assessment methods can be classified into the two groups of invasive and noninvasive ones. The most widely used method among the current non-invasive tests employed in research settings is flow-mediated dilation (FMD). This technique measures endothelial function by inducing reactive hyperemia via the temporary arterial occlusion and measuring the resultant relative increase in the blood vessel diameter via ultrasound. The high price and large size of the device, and being operator dependent are the limitation of this method. In this work, we propose using the photoplethysmogram (PPG) signal to overcome the limitations associated with the ultrasound technique. Studies show that PPG is affected by the endothelial function. In addition to the available dataset, we performed data acquisition for further analysis by recording the PPG signal during FMD and also during the hand lowering test to study the auto regulation effect. The Photoplethysmogram AC signal amplitude changes are modeled after flow-mediated dilation in healthy and diabetic subjects by AR model of order 2, and the results show 80% accuracy. The PPG pulse was modeled by a superposition of two Rayleigh pulses and by a superposition of a Gaussian and a Rayleigh pulses resulting in the fitness of 94.4% and 94.2% respectively. The error in calculating extracted features from the PPG signal does not exceed 7.5%. The results show that the Gaussian-Rayleigh model performance is better in PPG type 4 in comparison to the Rayleigh-Rayleigh model while the Rayleigh-Rayleigh model performs better for PPG type 1 (p<0.05). The best result of classifying normal coronary and 3VD subjects in both lowering and FMD tests is 86% accuracy
  9. Keywords:
  10. Modeling ; Flow Mediated Dilation ; Endothelial Function ; Photoplethysmography ; Hand Lowering Test

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