A decision support system for electrode shaping in multi-pad FES foot drop correction

Abstract

BackgroundFunctional electrical stimulation (FES) can be applied as an assistive and therapeutic aid in the rehabilitation of foot drop. Transcutaneous multi-pad electrodes can increase the selectivity of stimulation; however, shaping the stimulation electrode becomes increasingly complex with an increasing number of possible stimulation sites. We described and tested a novel decision support system (DSS) to facilitate the process of multi-pad stimulation electrode shaping. The DSS is part of a system for drop foot treatment that comprises a custom-designed multi-pad electrode, an electrical stimulator, and an inertial measurement unit.MethodsThe system was tested in ten stroke survivors (3–96 months post stroke) with foot drop over 20 daily sessions. The DSS output suggested stimulation pads and parameters based on muscle twitch responses to short stimulus trains. The DSS ranked combinations of pads and current amplitudes based on a novel measurement of the quality of the induced movement and classified them based on the movement direction (dorsiflexion, plantar flexion, eversion and inversion) of the paretic foot. The efficacy of the DSS in providing satisfactory pad-current amplitude choices for shaping the stimulation electrode was evaluated by trained clinicians. The range of paretic foot motion was used as a quality indicator for the chosen patterns.ResultsThe results suggest that the DSS output was highly effective in creating optimized FES patterns. The position and number of pads included showed pronounced inter-patient and inter-session variability; however, zones for inducing dorsiflexion and plantar flexion within the multi-pad electrode were clearly separated. The range of motion achieved with FES was significantly greater than the corresponding active range of motion (p < 0.05) during the first three weeks of therapy.ConclusionsThe proposed DSS in combination with a custom multi-pad electrode design covering the branches of peroneal and tibial nerves proved to be an effective tool for producing both the dorsiflexion and plantar flexion of a paretic foot. The results support the use of multi-pad electrode technology in combination with automatic electrode shaping algorithms for the rehabilitation of foot drop.Trial registrationThis study was registered at the Current Controlled Trials website with ClinicalTrials.gov ID NCT02729636 on March 29, 2016.

Optimization of Semiautomated Calibration Algorithm of Multichannel Electrotactile Feedback for Myoelectric Hand Prosthesis

“…As shown in the second column of Table 2, the high correlation values confirm the existence of individual patterns. Such result concurs with [21] confirming existence of individual electrotactile maps and are also in the accordance with the findings described in [28], describing temporal variability of sensitivity to electrical stimulation.…”

“…A drawback of electrotactile stimulation, amplified in multipad (array) systems, is the variability of elicited sensations. Even though sensitivity to electrotactile stimulation has some topological regularity [21], when observed on the level of precision needed for sensory substitution, significant intrasubject and temporal variability is observed [21, 22, 27, 28]. An additional concern is the significant overlap of preferred and uncomfortable amplitude ranges between different subjects as described in [21].…”

Electrode placement on the forearm for selective stimulation of finger extension/flexion

“…In future, we intend to develop a specific electrode array based on the shape and distribution of stimulation points detected in this study for selective stimulation of finger extension/flexion. Then, an iterative learning algorithm and sensor feedback may be used to identify the stimulation points that selectively activate individual finger and to control stimulating pulse output [ 39 – 40 ]. The frontend circuit of the stimulator should be further improved on the basis of the multi-pad wearable selective FES so that the current output resolution could be consistent with the research requirements.…”

A foot drop compensation device based on surface multi-field functional electrical stimulation—Usability study in a clinical environment

“…Run a calibration iteration 22 adapting the amplitude to the subject’s comfort with frequency and pulse-widths set to 35 Hz and 250 µs, respectively.…”