Modeling the Endothelial Function in the Brachial Artery Using Photoplethysmography

Mashayekhi, Ghoncheh | 2014

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 47677 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Zahedi, Edmond; Jahed, Mehran
  7. Abstract:
  8. Flow Mediated Dilation (FMD) is a non-invasive method for endothelial function assessment providing an index extracted from ultrasonic B-mode images. Although utilized in the research community, the difficulty of its application and high cost of ultrasonic device prevent it from being widely used in clinical settings. In this study we show that substituting the ultrasonic device with more easily handled and low cost photoplethysmography and electrocardiography is possible. We introduce new indices based on the photoplethysmogram (PPG) and electrocardiogram (ECG) and show that they are correlated with the ultrasound-based FMD index. To this end, conventional ultrasound FMD test was carried out whereas PPG and ECG were simultaneously recorded from 20 healthy volunteers (13 M, 7 F) in the age range of 23-32 years. Our results show a significant correlation between our proposed index and ultrasound FMD (R = 0.77, p<0.00001) in comparison to previously used indices (R = 0.48, p: N.S). Compared to conventional FMD, the proposed method is low cost and does not require any special operator skills. Hence it may be easily utilized as a screening tool in locations deprived from high-end ultrasound imaging devices. Although many experimental studies are conducted to understand the effect of different parameters on FMD, an analytical model has not yet been developed. In this study, a complete model is proposed for FMD where the effect of cuff occlusion is taken into account using a multi-branched arterial tree. Blood circulation is modeled through 64 lumped parameter segments for large arteries and 30 for peripheries. Auto-regulation mechanisms as endothelial, myogenic and metabolic are modeled using data from the literature and integrated into the systemic circulation. To validate the model, the data from the literature and our own experiments are used. The model outputs for the extracted index from PPG and FMD index are 97% and 10% respectively which are in the range of our experimental data which are 89 ± 54 % and 12± 4 % .We submit that this model can assist in quantification of the whole FMD procedure and investigating the response to the variation of each parameter
  9. Keywords:
  10. Flow Mediated Dilation ; Metabolic Regulation ; Myogenic Regulation ; Endothelial Function ; Autoregressive Process ; Reactive Hyperemia

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