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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
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
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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