abstract our client desires a device to detect the electrical activity of the bladder during the...
TRANSCRIPT
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 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 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 Epithelium Lamina propria Detrusor muscle
• Provides force required to void
• Three layers of smooth muscle
Perivesical soft tissue
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 Noninvasive method Store and print signal/data Applicable to males and females Compatible with urodynamic tests Accurate Juxtapose pressure and electrical
signals
Previous Research Netherlands study
• Six surface electrodes
• Extensive digital signal processing
• Inconclusive results
Sample Recording
Design Alternatives Electrode Design
• Memory Alloy
• Constellation
• Suction
• Needle Electrode Placement
• Vaginal
• Rectal
• Urethral
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 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
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
Future Work Create protocol Fine tune the circuit Obtain a clear signal Develop computer software Test extensively
• Clinical Setting
• Statistical Analysis data
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