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. The authors 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 maximum current of ±4.0 mA with a resolution of 2 μA. 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 stimulator was evaluated in first animal experiments. Electrical nerve stimulation was successfully performed with current pulses of different shapes