Stimulator design and subsequent stimulation parameter optimization for controlling micturition and reducing urethral resistance

An implantable computerized electrical stimulation system designed to induce bladder evacuation in animal models (dogs) after spinal cord transection has been realized and evaluated. This fully programmable system is based on a handheld device and generates a wide range of stimuli through a multichannel implantable miniaturized stimulator. Using the new bladder stimulator and inducing reversible fatigue to the external sphincter via the pudendal nerve enables one to reduce the bladder outlet resistance, resulting in the proper emptying of the bladder during stimulation without the need for sacral nerve rhizotomies and the pudendal nerve neurectomies. Four chronically affected dogs were studied to determine the optimal stimulation parameters for inducing a sphincter fatigue that would reliably empty the bladder for the duration of the experiment. These parameters were: maximum amplitude of 1.5 mA/spl plusmn/0.5 SD, stimuli composed of a high frequency signal of 200 Hz/spl plusmn/50 SD modulated by a low frequency signal of 10 Hz/spl plusmn/5 SD, pulse width controlled by a duty-cycle of 20%/spl plusmn/10 SD, sacral nerve stimulation of 50 s/spl plusmn/25 SD and fatiguing duration of 20 s/spl plusmn/5 SD.