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Pressure-Sensing Catheter Calibration

Pressure-Sensing Catheter Calibration. March 9, 2007. Team Members: Danielle Ebben Anita Zarebi Anthony Wampole Erik Yusko Marty Grasse. Client: Nancy Sweitzer, M.D. Colette Wagner. Advisor: William Murphy, Ph.D. Outline. Problem Statement Background Design Constraints

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Pressure-Sensing Catheter Calibration

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  1. Pressure-Sensing Catheter Calibration March 9, 2007 Team Members: Danielle Ebben Anita Zarebi Anthony Wampole Erik Yusko Marty Grasse Client: Nancy Sweitzer, M.D. Colette Wagner Advisor: William Murphy, Ph.D.

  2. Outline • Problem Statement • Background • Design Constraints • Status Update • Acrylic Pressure Chamber • Measurement and Control Systems • Future Direction

  3. Problem Statement In order to accurately measure internal blood pressures, a properly calibrated pressure sensitive cardiovascular catheter may be used. The current techniques for calibrating the catheter are unreliable, which causes concern about the validity of the test results. The goal of the project is to devise a testing system which more reliably calibrates and verifies the accuracy of the catheter in both atmospheric tests and tests which simulate internal bodily conditions.

  4. Project Background • Catheters used to measure blood pressure inside the heart • Clinical trials in progress • Catheter pressure readings inconsistent • Calibration method of manufacturer unknown • Need an effective way to calibrate the pressure transducers on the catheter www.healthsystem.virginia.edu

  5. Design Constraints • Both atmospheric and saline environments • Accuracy to +/- 2 mmHg • Able to achieve 200 mmHg; damage-resistant to 300 mmHg • Temperature control • Cost < $300

  6. Design Solution • Air/water tight container • Partially filled with saline • Pressure sensor mounted in wall • Air pump compresses air in the top of the container • Pressure is transferred to saline • Operator enters desired pressure • Pressure maintained by feedback from sensor to pump • Compare catheter pressure readings to container pressure

  7. Status at End of Semester • Machined container out of acrylic • Attempted to seal with O-ring and cork gasket • Seal around top edge leaky • Donated pump did not generate enough pressure • Feedback loop and temperature control not yet incorporated

  8. Box Alterations • Reduced height • 2 x 4 x 18 vs. 4 x 4 x 18 • Reduces amount of force • Added stability • Screws • Horizontal and Vertical Struts • Completely seal container

  9. Additions Due To Sealing • Use of sheath system to thread catheter • Filling port • Over-Pressure valve Sheath Catheter Swagelok

  10. Measurement & Control Systems PC Visual Basic High Current Source Voltage Supply DAQ Differential Amplifier Two-Stage Amplifier SSR SSR Air Pump Pressure Transducer Thermocouple Nichrome Element Pressure Control Block Temperature Control Block

  11. Pressure Control Block PC Visual Basic • Pressure sensor • DAQ • Computer • Program • Voltage converted to pressure • Decide appropriate course of action Voltage Supply DAQ Differential Amplifier SSR Air Pump Pressure Transducer

  12. Pressure Control Block PC Visual Basic • Pressure sensor • DAQ • Computer • Program • Voltage converted to pressure • Decide appropriate course of action Voltage Supply DAQ Differential Amplifier SSR Air Pump Pressure Transducer

  13. Heating Element: nickel chromium wire Two Stage amplifier: Differential amp with cold junction compensation Pure gain amp PC in turn reads/controls a current flow Temperature Control Block PC Visual Basic High Current Source DAQ Two-Stage Amplifier SSR Thermocouple Nichrome Element

  14. Acrylic Pressure Chamber Complete structural stabilization Machine nichrome wire path Measuring and Control Systems Implement amplifier circuits and power supplies Calibration Protocol Write a calibration/validation protocol for use Future Direction

  15. Questions?

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