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Abstract

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.


Motivation

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


Problem statement

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


Bladder composition

Bladder Composition

  • Epithelium

  • Lamina propria

  • Detrusor muscle

    • Provides force required to void

    • Three layers of smooth muscle

  • Perivesical soft tissue


Abstract 3294064

LALA


Micturition

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


Client requirements

Client Requirements

  • Noninvasive method

  • Store and print signal/data

  • Applicable to males and females

  • Compatible with urodynamic tests

  • Accurate

  • Juxtapose pressure and electrical signals


Previous research

Previous Research

  • Netherlands study

    • Six surface electrodes

    • Extensive digital signal processing

    • Inconclusive results

      Sample Recording


Design alternatives

Design Alternatives

  • Electrode Design

    • Memory Alloy

    • Constellation

    • Suction

    • Needle

  • Electrode Placement

    • Vaginal

    • Rectal

    • Urethral


Final design

Final Design

  • Internal and External Electrodes

    • Obtain signal

    • Reduce noise

  • EMG Circuit

    • Amplify and filter signal

    • Reject DC offset

  • Digital Oscilloscope

    • Display signal


Motion artifact

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


Emg circuit

EMG Circuit

  • Gain: 1775

  • High pass frequency: 60.2 Hz

  • Low pass frequency: 0.005 Hz

  • CMRR: 105.54 dB


Emg circuit diagram

EMG Circuit Diagram


Electrodes

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


Digital output device

Digital Output Device

  • Digital Oscilloscope

    • Storage

    • Real-time viewing capacity


Preliminary testing catheter electrode

Preliminary Testing: Catheter Electrode

Signal measured from a sinusoidal input


Preliminary testing surface electrodes

Preliminary Testing: Surface Electrodes

Signal measured during micturition


Future work

Future Work

  • Create protocol

  • Fine tune the circuit

  • Obtain a clear signal

  • Develop computer software

  • Test extensively

    • Clinical Setting

    • Statistical Analysis data


References

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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