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Nurullah Arslan Industrial Engineering & Graduate Institute of Sciences and Engineering

Biofluids & Cell Mechanics Laboratory. THE QUANTIFICATION OF TURBULENCE INSIDE AN ARTERIO-VENOUS GRAFT UNDER STEADY AND PULSATILE FLOW CONDITIONS. Nurullah Arslan Industrial Engineering & Graduate Institute of Sciences and Engineering. Arteriovenous Grafts Hemodialysis Patients.

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Nurullah Arslan Industrial Engineering & Graduate Institute of Sciences and Engineering

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  1. Biofluids& Cell Mechanics Laboratory THE QUANTIFICATION OF TURBULENCEINSIDE AN ARTERIO-VENOUS GRAFT UNDER STEADY AND PULSATILE FLOW CONDITIONS Nurullah Arslan Industrial Engineering & Graduate Institute of Sciences and Engineering

  2. Arteriovenous Grafts Hemodialysis Patients Arterial Anastomosis VenousAnastomosis Basilic Vein Artery PTFE graft

  3. 19% 4% 11% Distribution of Stenosis Kanterman et al., (1995) 67Patients 49%

  4. FINANCIAL REPORT END STAGE RENAL DISEASE (ESRD) HEALTH SUBCOMMITTE HEARING (APRIL 3, 1995 Washington, DC.) IN 1995, MEDICARE IS EXPECTED TO SPEND NEARLY $8 BILLION, OR OVER 4% OF ALL TOTAL SPENDING ON OVER 200,000 ESRD PATIENTS. THAT IS ABOUT $40,000 PER BENEFICIARY

  5. MOTIVATIONImprove Patency rate • Repeated reconstruction of the AV graft is expensive and uncomfortable for the patient • A better understanding of the fluid dynamic environment may help understand the causes of graft failure

  6. NOMENCLATURE PVS Arterial Anastomosis Venous Anastomosis DVS PTFE Graft

  7. PICTURE OF A REAL CONNECTION FROM A SURGERY

  8. LITERATURE REVIEW COLOR DOPPLER ULTRASOUND MEASUREMENTS Fillinger et al. (1991) • replace or revise the vascular access every three years in over half of their of patients • indicated turbulence (tissue vibration) and Reynolds number to be well correlated with intimal-thickening at the venous anastomosis

  9. LASER DOPPLER ANEMOMETER MEASUREMENTS AND FLOW VISUALIZATION STUDIES (SHU ET AL. 1991) • A realistic model geometry of A-V graft • Velocity profiles • Implicate the stagnation point and separation region • Poor wall shear stress measurements • No turbulent measurements

  10. TURBULENCESTUDIES • Turbulent measurements in straight pipes(Laufer et al. 1954) • The effects of turbulence on blood flow in constricted tubes(Deshpande et al., 1980, Jones et al., 1985, Kehoe et al., 1990) • Red blood cell damage caused by high Reynolds stresses

  11. OBJECTIVE • To determine the distribution of turbulence and Reynolds stresses • To define the critical regions such as separation region, stagnation point, and high turbulent region within the venous anastomosis of an A-V graft

  12. METHODS • Laser Doppler anemometry measurements inside an in vitro upscaled model of the venous anastomosis • Steady flow experiments representative of mean flow conditions (Reynolds number) • Newtonian fluid, rigid model

  13. COLOR DOPPLER ULTRASOUND MEASUREMENTS TAKEN FROM AN A-V GRAFT INSIDE A HUMAN PATIENT

  14. Graft DVS PVS

  15. IN VIVO MEASUREMENTS Doppler Ultrasound PVS PTFE graft 0.50 0.67 Diameter (cm) Mean Velocity (cm/s) 110 94 Peak Velocity (cm/s) 390 170 Mean Flowrate* (ml/sec) 33 (~2 l/min) 22 Peak Flowrate* (ml/sec) 76 59 (~3.5 l/min) * Flowrate were computed assuming flat velocity profile

  16. IN VIVO MEASUREMENTS PVS PTFE graft 1900 1700 Re # (mean) 3400 5800 Re # (peak) 4.0 Womersley # 5.3 Mean WSS (dynes/cm2) 39 63

  17. EQUATIONS Reynolds number Womersley number Wall shear stress Q=AV Flow Rate Properties of blood

  18. EXPERIMENTAL SETUP Argon-Ion laser 750mW Downstream tank Upstream Tank LDA probe Radiator Heater Test section Fluid: 42% Water 58% Glycerin Pump

  19. LASER DOPPLER ANEMOMETER OPTIMUM PARAMETER SELECTION FOR TURBULENT MEASUREMENTS

  20. The measurement locations in the bifurcation plane and the plane which is perpendicular to bifurcation plane (x sign shows the measurement points in the vertical direction)

  21. RESULTSEXERCISE CONDITION FOR GRAFT(PVS:DVS=100:0)

  22. VECTOR PLOTS FOR Re=650 and 1000

  23. VECTOR PLOTS FOR Re=2000 and 2300

  24. URMS VALUES FOR Re=650 and 1000

  25. URMS VALUES FOR Re=2000 and 2300

  26. VRMS VALUES FOR Re=650 and 1000

  27. VRMS VALUES FOR Re=2000 and 2300

  28. Reynolds stress(u’v’) VALUES FOR Re=650 and 1000

  29. Reynolds stress(u’v’) VALUES FOR Re=2000 and 2300

  30. RESULTSHEMODIALYSIS CONDITION(PVS:DVS=90:10)

  31. VECTOR PLOTS FOR Re=1000 and 1500

  32. VECTOR PLOTS FOR Re=2000 and 2300

  33. URMS VALUES FOR Re=1000 and 1500

  34. URMS VALUES FOR Re=2000 and 2300

  35. Reynolds stress(u’v’) VALUES FOR Re=1000 and 1500

  36. Reynolds stress(u’v’) VALUES FOR Re=2000 and 2300

  37. NEAR WALL VELOCITY MEASUREMENTS FOR Re=2300 (Separation region)

  38. CONCLUSIONS Toe side of the PVS: • high turbulence (29%) , high Reynolds stresses (1263 dyne/cm2), strong secondary flow, and a large separation region • is often sited as the location of stenosis formation in A-V grafts

  39. FUTURE WORK • use a more physiological geometry • repeat measurements under pulsatile flow conditions • track the condition of patient’s graft

  40. Midplane Velocity Vectors at Re=650

  41. Midplane Velocity Vectors at Re=1000

  42. Turbulence Intensity RMS of Axial Velocity Component at Re=650

  43. In Vivo flow wave form at Graft and DVS (Graft:DVS=90:10)

  44. Turbulent Fluctuation at P12 for Pulsatile flow Re=2000 for steady flow and Remax=2021 for pulsatile flow

  45. Power spectrum analysis at high turbulent region (p12) for pulsatile flow

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