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Photoplethysmography-Based System for Atrial Fibrillation Detection During Hemodialysis

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D. Stankevicius , A. Petrenas, A. Solosenko, M. Grigutis, T. Januskevicius, L. Rimsevicius, V. Marozas. Photoplethysmography-Based System for Atrial Fibrillation Detection During Hemodialysis. In IFMBE Proceedings, vol. 57, 14th Mediterranean Conference on Medical and Biological Engineering and Computing (MEDICON 2016), pp. 79-82, Paphos, Cyprus, 31 Mar. – 2 Apr. 2016

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Photoplethysmography-Based System for Atrial Fibrillation Detection During Hemodialysis

  1. 1. Photoplethysmography-based system for atrial fibrillation detection during hemodialysis Dainius Stankevicius, A. Petrenas, A. Solosenko, M. Grigutis, T. Januskevicius, L. Rimsevicius, and V. Marozas dainius.stankevicius@ktu.lt Vilnius university hospital SANTARIŠKIŲ KLINIKOS
  2. 2. Introduction (1) Hemodialysis: – 350 000 people in the EU – 5400 dialysis centers in the EU – 60 % of chronic kidney disease patients – 3 times per week – 4 hours long 1/20
  3. 3. Introduction (2) Atrial fibrillation (AF): – The most common arrhythmia – 33 million people around the world – Risk of stroke and heart failure Connection: – Hemodialysis increases risk of developing AF – AF occurs during hemodialysis – Related to changes in fluid balance 2/20
  4. 4. Research question Can we detect AF during hemodialysis in an unobtrusive and still reliable way? 3/20
  5. 5. Proposal • Electrocardiography is encumbering • Photoplethysmography might be a solution – Definitely less obtrusive! – Also less reliable... • A system consisting of: – Specialized low power device – Embedded algorithm to run the detection 4/20
  6. 6. We have built a device • ARM Cortex-M0, 16 MHz, 16 kB SRAM • PPG sampling at 250 Hz • 24-hour battery life 5/20
  7. 7. Methodology: Start ppg(n) 6/20
  8. 8. Raw PPG 7/20
  9. 9. Methodology: Preprocessing ppg(n) Low pass filter fc LMS w1...w10 m + - x(n) = 1 ppgl(n) ppga(n) y(n) 8/20
  10. 10. Raw & Preprocessed PPGs 9/20
  11. 11. Methodology: SSF SSF N ppga(n) s(n) 10/20 Slope Sum Function (SSF):
  12. 12. PPG and SSF 11/20
  13. 13. Methodology: Thresholding SSF N Thresholding T, Tk max{s(n)} arg[max{s(n)}] median{p(m),...,p(m-4)} i(m)-i(m-1) ppga(n) s(n) T p(m) i(m) ∆i(m) st(n)SSF N ppga(n) s(n) 12/20
  14. 14. Thresholding and peak-to-peak 13/20
  15. 15. Methodology: AF detector i(m)-i(m-1) Low complexity AF detector a d t i(m) ∆i(m) O(m) 14/20
  16. 16. Methodology: overall Low pass filter fc LMS w1...w10 m SSF N Thresholding T, Tk max{s(n)} arg[max{s(n)}] median{p(m),...,p(m-4)} i(m)-i(m-1) + - Low complexity AF detector a d t x(n) = 1 ppg(n) ppgl(n) ppga(n) s(n) T p(m) i(m) ∆i(m) O(m) st(n) y(n) 15/20
  17. 17. Testing: hardware-in-the-loop Real environment Simulated environment Pre-recorded PPG with AF Raw data file saved in microSD card Normal PPG sampling routine... Read PPG sample PPG hardware 16/20
  18. 18. Results 0 50 100 150 200 -1 0 1 2 0 50 100 150 200 100 200 300 400 0 50 100 150 200 0 1 2 0 50 100 150 200 0 1 Outa Outb Threshold Time, s 0 50 100 150 200 0 5000 17/20
  19. 19. Conclusion The proposed system has a potential to be applied for an unobtrusive real-time AF detection using solely the photoplethysmogram. 18/20
  20. 20. Future directions • Introduce signal quality metrics • Introduce morphology-based features • Determine the optimal placement of the device 19/20
  21. 21. Acknowledgment • This work was supported by CARRE (No.611140) project, funded by the European Commission Framework Program 7. • CARRE – CARdio REnal disease • http://www.carre-project.eu 20/20

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