A Functional Electrical Stimulator to Enable Grasping Through Wrist Flexion

Functional electrical stimulation is an assistive technique that utilizes electrical discharges to produce functional movements in patients suffering from neurological impairments. In this work, a biphasic, programmable current- controlled functional electrical stimulator system is designed to enable hand grasping facilitated by wrist flexion. The developed system utilizes an operational amplifier based current source and is supported by a user interface to adjust stimulation parameters. The device is integrated with an accelerometer to measure the degree of stimulated movement. The system is validated, firstly, on two passive electrical loads and subsequently on four healthy volunteers. The device is designed to deliver currents between 0-30mA, and the error between the measured current and simulated current for two loads were -0.967±0.676mA and -0.995±0.97mA. The angular data from the accelerometer provided information regarding variations in movement between the subjects. The architecture of the proposed system is such that it can, in principle, automatically adjust the parameters of simulation to induce the desired movement optimally by measuring a stimulated movement artifact (e.g., angular position) in real time.

I Want to Control Your Move: Human-Human Interface (HHI) Neuromuscular Electrical Stimulator (NMES)

Neuromuscular electrical stimulation (NMES) has been widely used in rehabilitation hubs to restore or replace the motor function of individuals who have upper neuron damage such as stroke and spinal cord injury. However, the utilization of sensors in NMES is limited and results in the lack of data for upper limb movement analysis. The proposed system implemented NMES integrated with human-to-human interface (HHI) in the rehabilitation process for stroke patients. The therapist (controller) can coach the motion of patients (subject) by injecting his own signal for patients to follow. Ten (10) subjects were tested with five (5) repeating trials. The EMG value was extracted from the finger flexion and extension at the controller side, then injected into the control unit for further stimulation of the subject. In order to evaluate the repeating motion by the subject, an accelerometer was attached to the finger. Performance evaluation of the subject was executed by comparing the flexion angle with the controller side. The result showed that the error of the system was less than 10.29 % for the first trial and gradually reduced to 1 % after 5 trials.

Chronic Pain Alters Somatosensory Evoked Potentials and Paired-pulse Inhibition in Athlete

Injuries are inevitable for athletes, and when injuries end up causing chronic pain, they usually force athletes to withdraw from training. Chronic pain is known to be caused by plastic changes in the brain; thus, the purpose of this study was to assess the somatosensory evoked potential (SEP) and the paired-pulse inhibition (PPI) in athletes suffering from chronic pain as compared to pain-free athletes. Twenty track and field (T&F) athletes, that were also undergraduate students, were recruited for this study. These athletes (12 men; 8 women) were divided into two groups of 10 based on their self-reporting of actively experiencing chronic pain (defined as pain that persisted for more than 3 months) or not. Both SEP and PPI in the primary somatosensory cortex (SI) were elicited by constant current square-wave pulses (of 0.2 ms duration) that were delivered to the right median nerve by an electrical stimulator through a surface bar electrode with a cathode proximal. Paired-pulse stimulation was set at interstimulus intervals of 30 and 100 ms. Subjects were randomly presented with 1,500 single- and paired-pulse stimuli at 2 Hz. Our measurements demonstrated a trend toward a lower N20 and P25 amplitude as well as a disinhibition of the PPI_30 ms in the athletes suffering from chronic pain. These findings suggest that chronic pain may modulate excitatory and inhibitory function of the SI in athletes as well as in patients suffering from complex regional pain syndrome or fibromyalgia.

A Generic Sequential Stimulation Adapter for Reducing Muscle Fatigue during Functional Electrical Stimulation

Background: Clinical applications of conventional functional electrical stimulation (FES) administered via a single electrode are limited by rapid onset neuromuscular fatigue. “Sequential” (SEQ) stimulation, involving the rotation of pulses between multiple active electrodes, has been shown to reduce fatigue compared to conventional FES. However, there has been limited adoption of SEQ in research and clinical settings. Methods: The SEQ adapter is a small, battery-powered device that transforms the output of any commercially available electrical stimulator into SEQ stimulation. We examined the output of the adaptor across a range of clinically relevant stimulation pulse parameters to verify the signal integrity preservation ability of the SEQ adapter. Pulse frequency, amplitude, and duration were varied across discrete states between 4 and 200 Hz, 10 and100 mA, and 50 and 2000 μs, respectively. Results: A total of 420 trials were conducted, with 80 stimulation pulses per trial. The SEQ adapter demonstrated excellent preservation of signal integrity, matching the pulse characteristics of the originating stimulator within 1% error. The SEQ adapter operates as expected at pulse frequencies up to 160 Hz, failing at a frequency of 200 Hz. Conclusion: The SEQ adapter represents an effective and low-cost solution to increase the utilization of SEQ in existing rehabilitation paradigms.

Selective electrical stimulation with currentfield modulation

Selective electrical stimulation using a multielectrode array is a promising technique that can potentially bring electrical stimulation treatment modalities a step forward. A microcontroller-controlled electrical stimulator system delivering a single pulse was designed, suitable for current-field modulation. The goal is to make electrical stimulation with surface electrodes more specific. A graphical user interface (GUI) was developed to control stimulation parameters and current-field within a multi-electrode array wirelessly. The stimulator generates arbitrary biphasic waveforms with a 5-bit resolution and high temporal precision (<10 μs) and was demonstrated to stimulate posterior lumbar root fibers in transcutaneous spinal cord stimulation (tSCS) treatment selectively. Current-field modulation throughout a sixteen-electrode array was achieved. The system has the goal to improve control of stimulation conditions in electrophysiological studies and time-dependent and site-specific stimulation patterns for neuromodulation applications. A novel feature is the current-field modulation ability of the stimulator for surface electrode arrays.

A generic sequential stimulation adapter for reducing muscle fatigue during functional electrical stimulation

BackgroundClinical applications of conventional functional electrical stimulation (FES) administered via a single electrode is limited by rapid onset neuromuscular fatigue. “Sequential” (SEQ) stimulation, involving rotation of pulses between multiple active electrodes, has been shown to reduce fatigue compared to conventional FES. However, there has been limited adoption of SEQ in research and clinical settings.MethodsThe SEQ adapter is a small, battery-powered device that transforms the output of any commercially available electrical stimulator into SEQ stimulation. We examined the output of the adaptor across a range of clinically relevant stimulation pulse parameters to verify the signal integrity preservation ability of the SEQ adapter. Pulse frequency, amplitude, and duration were varied across discrete states between 4-200 Hz, 10-100 mA, and 50-2000 μs, respectively.ResultsA total of 420 trials were conducted, with 80 stimulation pulses per trial. The SEQ adapter demonstrated excellent preservation of signal integrity, matching the pulse characteristics of the originating stimulator within 1% error. The SEQ adapter operates as expected at pulse frequencies up to 160 Hz, with a noted failure mode at 200 Hz.ConclusionThe SEQ adapter represents an effective and low-cost solution to increase the utilization of SEQ in existing rehabilitation paradigms.