A Biofeedback Based Auto-Controlled Neurostimulator Design for Proper NCS Signal Acquisition and Measurement

This paper presents the design of a biofeedback based auto-controlled neurostimulator for acquiring nerve response. Nerve conduction study (NCS) employs an electrical stimulator that generates a stimulus to be applied over the skin of an underlying nerve. Conventional neurostimulator uses manual control of voltage or current to generate the nerve responses. It is observed that the stimulation for supramaximal response varies with subjects due to different skin resistances of the subjects. Such measurement needs repeated trials which is time consuming, irritating to subjects and often suffers difficulties in real-time applications. This study proposes a portable neurostimulator based on the skin resistance as bio-feedback parameter to control the stimulus. A custom made NCS setup is developed for experimental recording of real-time nerve signals and identified the best compound muscle action potential signal for generating optimal stimulus i.e., supramaximal stimulus (SS) manually. Then, mathematical models are investigated using real-time data and models are implemented in a microcontroller (µC) based stimulator. The µC triggers a pulse train of specific duty cycle to a buck converter for producing the required optimal voltage which is used as a SS across the electrodes. Online experimental results with new subjects show that the proposed design is efficacious and adaptable with safety.