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Finger Plethysmograph For Measuring Blood Resistivity

Finger Plethysmograph For Measuring Blood Resistivity. Client: John G. Webster, Ph.D Advisor: Thomas Yen, Ph.D. Team Tim Balgemann - Team Leader Lucas Vitzthum - Communications Nick Harrison- BSAC Tyler Lark- BWIG. Outline. Background Problem Statement Theory Electrical

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Finger Plethysmograph For Measuring Blood Resistivity

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  1. Finger Plethysmograph For Measuring Blood Resistivity Client: John G. Webster, Ph.D Advisor: Thomas Yen, Ph.D. Team Tim Balgemann- Team Leader Lucas Vitzthum- Communications Nick Harrison- BSAC Tyler Lark- BWIG

  2. Outline • Background • Problem Statement • Theory • Electrical • Biological Concepts • Design Components • Circuit Design • Mechanical • Future Work

  3. Diabetes • Body’s inability to manage glucose levels • Prevalence is on the rise • 26.3 million in U.S. • $116 billion excess medical expenditures annually • No reliable non-invasive monitoring • Hypothesized that blood sugar levels may be correlated with blood resistivity

  4. Problem Statement • Design a finger plethysmograph to measure blood resistivity • Goals: • Build a mechanical device to secure finger • Design a circuit that allows data acquisition of blood impedance

  5. Electrical Theory • Four electrode impedance plethysmography • 2 electrodes pass current through finger • 2 electrodes measure voltage • Signal processing • Calculate impedance and resistivity from voltage output

  6. Biological Theory • High blood flow • RBCs align, current meets little resistance • Low blood flow • RBCs misalign, greater resistance • Impedance (ΔZ) results from this • Change in volume of artery • Saline solution cancels signal High Flow Low Flow

  7. Design Specifications • Circuit • Sensitivity • Adaptable measurement range (i.e. autoreset) • Digital filtering and signal processing • Mechanical Device • Motion artifacts • Minimal electrical signature

  8. Measuring change in blood resistivity Sample and Hold Filtering Current amplitude and frequency Data interpretation Circuitry Webster J. G., 1998

  9. Mechanical Design • Restrain Finger • Circulation • Conductive Voltmeter CurrentSource

  10. Restrain Designs Inflatable Cuff Bar Cage Mesh Cage Top Air in Side

  11. Future Work • Build prototype • Optimize saline solution • Current amplitude and frequency • Circuit component values • Testing • Clinical Trials

  12. References • Webster J. G., 1998. Measurement of flow and volume of blood Medical Instrumentation: Application and Design, 3rd Edition ed J G Webster (New York: John Wiley & Sons). • Rosenthal, J. H., An inductive plethysmograph for ambulatory ventilation measurement. • American Diabetes Association: http://www.diabetes.org/diabetes-statistics.jsp • World Health Organization: http://www.who.int/dietphysicalactivity/publications/facts/diabetes/en/

  13. Questions??

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