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Abstract

Abstract.

Thomas
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Abstract

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  1. Abstract Our client desires a device to detect the electrical activity of the bladder during the voiding process. The device will be used in a urodynamics lab in conjunction with diagnostic tools. The final design incorporates external and internal electrodes, an EMG circuit, and a digital oscilloscope.

  2. Motivation • Overactive Bladder (OAB): A sudden urge to urinate immediately followed by a bladder contraction, resulting in involuntary micturition • Affects 33 million Americans • May cause urinary incontinence • Limited treatment options • Disposable pads • Medication • Catheters

  3. Problem Statement • Bladder EMG has never been consistently detected • Frequency and magnitude of electrical signal are not well established • Pelvic bone and abdominal muscles distort/interfere with signal detection

  4. Bladder Composition • Epithelium • Lamina propria • Detrusor muscle • Provides force required to void • Three layers of smooth muscle • Perivesical soft tissue

  5. LALA

  6. Micturition • Urine exits the bladder through the urethra • Outflow is controlled by muscles called sphincters, which surround the urethra • The sphincters and pelvic floor muscles under the bladder keep the urethra closed • Micturition is initiated by the contraction of the detrusor and relaxation of the sphincter/pelvic floor muscles

  7. Client Requirements • Noninvasive method • Store and print signal/data • Applicable to males and females • Compatible with urodynamic tests • Accurate • Juxtapose pressure and electrical signals

  8. Previous Research • Netherlands study • Six surface electrodes • Extensive digital signal processing • Inconclusive results Sample Recording

  9. Design Alternatives • Electrode Design • Memory Alloy • Constellation • Suction • Needle • Electrode Placement • Vaginal • Rectal • Urethral

  10. Final Design • Internal and External Electrodes • Obtain signal • Reduce noise • EMG Circuit • Amplify and filter signal • Reject DC offset • Digital Oscilloscope • Display signal

  11. Motion Artifact • Fact: Netherland study recorded a 0.5 mV change during micturition • Problem: Surface electrodes can cause skin motion artifact greater than 0.5 mV • Question: Is the 0.5 mV signal from the bladder or a result of skin motion artifact? • Solution: Abrade the skin to eliminate skin motion artifact

  12. EMG Circuit • Gain: 1775 • High pass frequency: 60.2 Hz • Low pass frequency: 0.005 Hz • CMRR: 105.54 dB

  13. EMG Circuit Diagram

  14. Electrodes • External Electrode • Ag-Ag/Cl surface electrodes • Located above and below pubic bone • Internal Electrode • 1 mm diameter, 2.5 mm pellet • 10 mm silver wire • Sintered and re-useable • Inserted in 5 French catheter • Sealed with epoxy

  15. Digital Output Device • Digital Oscilloscope • Storage • Real-time viewing capacity

  16. Preliminary Testing: Catheter Electrode Signal measured from a sinusoidal input

  17. Preliminary Testing: Surface Electrodes Signal measured during micturition

  18. Future Work • Create protocol • Fine tune the circuit • Obtain a clear signal • Develop computer software • Test extensively • Clinical Setting • Statistical Analysis data

  19. References • Ballaro A, Mundy AR, Fry CH, and Craggs MD. Bladder electrical activity: the elusive electromyogram. BJU International, 2003. 92: 78-84. • “Catheters and Transducers.” Medtronic. • http://www.medtronic.com/neuro/mfd/consumables/acc_cat_2k1_trans.pdf September 25, 2003. • Kinder MV, van Waalwijk ESC, Gommer ED, and Janknegt RA. A non-invasive method for bladder electromyography in humans. Archives of Physiology and Biochemistry, 1998. 106: 2-11. • “Pelvic Soft Tissue Structures.” Barts and the London, Queen Mary’s school of Dentistry and Medicine. • http://www.mds.qmw.ac.uk/biomed/kb/grossanatomy/basic_anat/pelvic_soft.htm September 25, 2003. • Kinder MV, van Waalwijk ESC, Gommer ED, and Janknegt RA. A non-invasive method for bladder electromyography in humans. Archives of Physiology and Biochemistry, 1998. 106: 2-11. • “TECA NCS Disposable Surface Electrodes.” Oxford Instruments. http://www.oxford-instruments.com/MDCPDP346.htm September 25, 2003. • Paul Victorey, Biomedical Engineering Department, UW-Madison

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