Computer-based clinical instrumentation for processing and analysis of mechanically evoked electromyographic signals in the upper limb

A computer-based clinical instrument was developed to simultaneously acquire, process, display, quantify and correlate electromyographic (EMG) activity, resistive torque, range of motion (ROM), and pain responses evoked by mechanical stimuli (i.e. passive elbow extensions) in humans. This integrated multicahnnel system was designed around AMLAB analog modules and software objects called ICAMs. Each channel consisted of a time- and frequency-domain block, a torque and angle measurement block, an experiment number counter block and a data storage and retrieval block. The captured data in each channel was used to display and quantify: raw EMG, rectified EMG, smoothed rectified EMG, root-mean-squared EMG, fast Fourier transformed (FIT) EMG, and normalized power spectrum density (NPSD) of EMG. Torque and angle signals representing elbow extension measured by a KIN-COM(R) dynamometer during neural tension testing, as well as signals from an electronic pain threshold marker were interfaced to an AMLAB workstation and presented in one integrated display. Calibration was achieved by using low-level square and sine waves. Weight compensation was implemented by developing a special interface between the AMLAB and the KIN-COM dynamometer. Although this system was designed to specifically study the patterns and nature of evoked motor responses in Carpal Tunnel Syndrome (CTS) patients, it could equally well be modified to allow acquisition, processing and analysis of EMG signals in other studies and applications. In this paper, we describe an integrated system to simultaneously study and analyze the mechanically evoked electromyographic, torque and ROM signals and correlate various levels of pain to these signals.