AbstractOur 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

LALA

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

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

EMG Circuit Diagram

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 Oscilloscope

• Storage • Real-time viewing

capacity

Preliminary Testing: Catheter Electrode

Signal measured from a sinusoidal input

Preliminary Testing: Surface Electrodes

Signal measured during micturition

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