Client: Dr. Mark Reichelderfer, M.D.

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• Client Dr. Mark Reichelderfer, M.D.
• Dr. Adnan Said, M.D.
• Gastroenterology
• University of Wisconsin Hospital
• Advisor Aura Gimm, Ph.D.
• Department of Biomedical
  Engineering

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Team Members

• Bayley Denham
• Audrey Hale
• Hannah Kirking
• Katie Mantz
• Joel Rotroff
• Christine Weisshaar
• Kelly Williams
• Tiffany Zens

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ABSTRACT

• Esophageal strictures are a complication of
  gastro esophageal reflux disease. Strictures
  cause an array of clinical complications.
  Medical professionals are currently in need of a
  device that allows esophageal strictures to be
  characterized in terms of diameter and
  compliance. Previously, a device was created
  with the ability to create pressure vs. volume
  curves based upon the stricture. The goal of
  this project is to improve the current prototype
  and to design a device that can create standard
  pressure vs. volume curves. Eventually, medical
  professionals hope to be able to characterize
  strictures based on these curves and those
  collected from actual patients.

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PROBLEM STATEMENT

• Project consists of two design components
• Develop a device that measures both the
  compliance and radius of esophageal strictures.
  This device would be most helpful if it was
  similar to the current setup used.
• Create a model of the esophagus which could be
  used to test the new device and ensure its
  accuracy.

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BACKGROUND

• The esophagus is the muscular tube connecting the
  pharynx to the stomach. Its main job is to
  transport food to the stomach through small
  convulsions known as peristalsis.

Esophagus, MuscHealth.com The Online Resource.
www.muschealth.com. October 13, 2002.
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BACKGROUND

• Problems arise when the lower esophageal
  sphincter does not function properly and stomach
  acid leaks into the esophagus. The repeated
  exposure of the esophagus to this acid leads to
  the buildup of scar tissue known as a
  stricture.

Jackson Gastroenterology. Jackson
Gastroenterology Webpage Online. http//www.gica
re.com/pated/eiegesde.htm 10/08/02.
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BACKGROUND

• A normal esophagus is approximately 25 mm in
  diameter, but the buildup of scar tissue
  decreases this diameter. A reduction in diameter
  to 15 mm causes discomfort during eating and
  drinking and usually requires dilation. In
  extreme cases, strictures can reduce the diameter
  to a mere 2 mm.

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CURRENT TREATMENT

• The most common method used to treat strictures
  is dilation. In this process a balloon is slid
  down the esophagus to the stricture where the
  balloon is inflated by a hand-held gun to stretch
  the tissue.

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DESIRED DEVICE CRITERIA

• Similar in shape and method to the current device
• Graphically displays the instantaneous volume of
  the balloon versus the pressure within the
  balloon to help the doctor know when the
  stricture is safely dilated
• Thoroughly tested to ensure safety

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PROPOSED SOLUTION

• Double-barreled syringe
• Air-filled syringe used to derive volume using
  PVnRT
• Water-filled syringe used to derive pressure

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DESIGN CHALLENGES

• Graphing pressure vs. volume in real time
• The software used for testing, Biobench, is only
  able to graph each variable individually with
  respect to time.
• Inquires into Pasco, used by the Physics
  department, and Biopac, used by the Physiology
  and Biocore departments, were both unsuccessful.

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COMPLIANCE TUBING

• Latex tubes of different thicknesses and
  therefore different compliance values were formed
  by applying different amounts of liquid latex to
  a steel bar. (A red tube made of polyethylene
  plastic dip was created to represent very low
  compliance.)

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TESTING

• The balloon dilator was inserted into each of the
  different compliance tubes which were held at a
  constant length and tension by the tube-housing
  unit.

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TESTING

• The balloon was inflated using the gun.
• Measurements were collected on Biobench and
  exported to Microsoft Excel for analysis.

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RESULTS

• Data collected from the water-pressure sensor was
  converted to pressure in Pascals (Pa).
• Data collected from the air-pressure sensor was
  converted first to pressure and then to volume
  using the ideal gas law, PV nRT.
• Pressure versus volume graphs were created for
  each tube of different compliance.

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RESULTS Least Compliant

• For a tube of low compliance, a greater pressure
  is required to achieve a given volume.
• Compliance ?Volume/?Pressure
• The red tube was the least compliant, generating
  the highest pressure per volume.

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FUTURE WORK

• Real-time graphing is needed for the results to
  be useful during the procedure.
• Based on research, it appears that LabView could
  be used to perform real-time graphing.
• Device remains cumbersome and improvements could
  simplify use.

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FUTURE WORK

• Obtain a more accurate compliance range in order
  to fabricate tubing that more closely simulates
  the esophagus.
• Add a digital pressure sensor in place of the
  current gauge sensor on the gun.

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SPECIAL THANKS TO

• Rafael Chavez-Contreras, ChE professor
• Aura Gimm, BME advisor
• Bill Hagquist, experienced engineer
• Michelle Harris, Biocore lab director
• Andrew Lokuta, Physiology lab director
• Sanford Klein, ME professor
• Jeff Schowalter, ECE lab director
• Joe Sylvester, Physics lab director
• Paul Treichel, Chemistry professor

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REFERENCES

• Bernoullis Equation, Princeton University
  homepage. http//www.princeton.edu/asmits/Bicycle
  _web/Bernoulli.html October 15, 2002.
• Health Link. Medical College of Wisconsin
  Webpage Online. http//healthlink.mcw.edu/articl
  e/1010766575.html 10/10/02.
• McCabe W., Smith, J., and Harriott, P. Unit
  Operations of Chemical Engineering. 2001.
  McGraw Hill, Boston. Pgs. 222-228.