An Exploratory Investigation on the Use of Closed-Loop Electrical Stimulation to Assist Individuals with Stroke to Perform Fine Movements with Their Hemiparetic Arm

Abstract

Stroke is the leading cause of upper limb impairments resulting in disability. Modern rehabilitation includes training with robotic exoskeletons and functional electrical stimulation (FES). However, there is a gap in knowledge to define the detailed use of FES in stroke rehabilitation. In this paper, we explore applying closed-loop FES to the upper extremities of healthy volunteers and individuals with a hemiparetic arm resulting from stroke. We used a set of gyroscopes to monitor arm movements and used a non-linear controller, namely, the robust integral of the sign of the error (RISE), to assess the viability of controlling FES in closed loop. Further, we explored the application of closed-loop FES in improving functional tasks performed by individuals with stroke. Four healthy individuals of ages 27-32 years old and five individuals with stroke of ages 61-83 years old participated in this study. We used the Rehastim FES unit (Hasomed Ltd.) with real-time modulation of pulse width and amplitude. Both healthy and stroke individuals were tested in RISE-controlled single and multi-joint upper limb motions following first a sinusoidal trajectory. Individuals with stroke were also asked to perform the following functional tasks: picking up a basket, picking and placing an object on a table, cutting a pizza, pulling back a chair, eating with a spoon, as well as using a stapler and grasping a pen. Healthy individuals were instructed to keep their arm relaxed during the experiment. Most individuals with stroke were able to follow the sinusoid trajectories with their arm joints under the sole excitation of the closed-loop-controlled FES. One individual with stroke, who was unable to perform any of the functional tasks independently, succeeded in completing all the tasks when FES was used. Three other individuals with stroke, who were unable to complete a few tasks independently, completed some of them when FES was used. The remaining stroke participant was able to complete all tasks with and without FES. Our results suggest that individuals with a low Fugl-Meyer score or a higher level of disability may benefit the most with the use of closed-loop-controlled FES.

Keywords: FES; electrical stimulation; functional movements; stroke; upper limb.

Figure 1

System block diagram for biceps muscle stimulation. The joint angle was calculated using two appropriately positioned strap-on gyroscopes, which communicated with the PC via a data acquisition device (DAQ) through USB. The PC communicated with the RehaStim device via a serial USB connection. Stimulation of other muscles had an analogous setup, but with alternate placement of the gyroscopes and electrodes.

Figure 2

RISE controller block diagram.

Figure 3

Graphs of closed-loop FES when applied to various muscles for healthy and stroke individuals. (A) Biceps for a healthy volunteer (H2); (B) biceps for a volunteer with stroke (S1); (C) triceps for a healthy volunteer (H2); (D) triceps for a volunteer with stroke (S2); (E) infraspinatus for a healthy volunteer (H4); (F) infraspinatus for a volunteer with stroke (S1); (G) anterior deltoid for a healthy volunteer (H4); (H) anterior deltoid for a volunteer with stroke (S5); (I) pectoralis major for a healthy volunteer (H4); and (J) pectoralis major for a volunteer with stroke (S1).

Figure 4

Example of compound biceps (A) and infraspinatus (B) stimulation for a healthy participant, performing a motion analogous to pick and place for stroke participants. The two motions occurred simultaneously.

Figure 5

Example of successful compound biceps (A) and infraspinatus (B) stimulation for a stroke participant performing the functional task “pick and place an object.” The two motions occurred simultaneously, with the joint trajectory of the participant attempting the same task without FES also shown in purple for the infraspinatus.

Figure 6

Task assistance performance of FES with increasing Fugl–Meyer score.

Figure 7

Performance of functional tasks associated with wrist dorsiflexion through FES application. The same subject attempting the same task without FES is also shown for comparison. (A) S5 doing “use a stapler” task. (B) S1 doing “grasp a pen” task.