A modular multichannel stimulator for arbitrary shaped current pulses for experimental and clinical use in FES

Functional electrical stimulation (FES) applies non-square shaped current pulses for selective activation of thin nerve fibers. We developed a multichannel stimulator for the use in FES that enables the application of biphasic, arbitrary shaped current pulses. A high resolution of fast signal portions was combined with the demand of data reduction using a non-equidistant description of the stimulation pulses. The system was realized in a host-client architecture and could be expanded to multiple clients. It operates alternatively as plug-in card via the ISA-bus of a personal computer or as a stand alone device via a serial interface (RS 232 C). Each stimulation channel delivers a maxinium current of +- 4.0 mA with a resolution of 2 my A. Additionally, a measurement unit was implemented to monitor the electrode impedance and an electrode break. A graphical user interface allows an easy and safe operation to control the system. The stimulation was evaluated in first animal experiments. E lectrical nerve stimulation was succesfully performed with current pulses of different shapes.