Wireless Control of Functional Electrical Stimulation Systems

Abstract: With the assistance of crutches and functional electrical stimulation (FES), we are able to restore standing and simple gait in some spinal cord injured (SCI) patients. In present rehabilitative systems, the patient divides the gait cycle into stance and swing phases via pushbuttons mounted on the handles of the crutches, which are hardwired to the functional electrical stimulator. The surfacemount technology based telemetry system, which makes use of the radiofrequency medium at 40 MHz, was developed to provide wireless control of the FES system. Signals from crutch pushbuttons were coded and transferred from the transmitter to the receiver. The receiver was firmly attached to the patient's waist and was connected to the stimulator.     

An Artificial Neural System for Closed Loop Control of Locomotion Produced via Neuromuscular Electrical Stimulation

Abstract: The use of neuromuscular electrical stimulation for restoration of gait in spinal cord injured subjects has been seriously pursued by many investigators for the past 15 years. By and large, however, systems to date require the intervention of a person, be it the patient or an observer, and are restricted to control of stimulation onset and termination. Further, existing systems are not adaptable to environmental and patient variations. This work proposes a system that relies on neural computing to determine proper muscle activation patterns from biome-chanical signals. The intelligent system is trained to perform gait under supervision, after which it can be used to control muscle stimulation in an unknown environment.
Computer simulations suggest that the best neural architecture for control of gait is a neural network including units corresponding to movement history. Separate networks for the stance and swing phases, respectively, were found to work better than a single neural network trained on the entire gait cycle. The artificial neural device proposed here also includes a voice recognition system that will allow for voluntary locomotion. A safety circuit has been designed to preclude acceptance of unwanted vocal commands in the latter system.     

Portable Closed Loop Feedback System for Control of the Blood Glucose Level in the Pig

To establish the difference in glucose consumption of healthy compared to diabetic pigs, a transportable system for the feedback control of insulin and glucose was used in conscious pigs. The system for controlling glucose levels, as well as glucose consumption, was easy to use and adjusted smoothly to rapid changes in insulin level. Five days prior to the first day of experiment, healthy animals were prepared with intravenous jugular catheters tunnelled subcutaneously to the neck. On the first day of experiment, measurements of glucose were continuously taken before and after food ingestion. The animals were rendered diabetic after 2 days using Alloxan and streptozotocin. The measurements were then repeated. To be able to obtain constant glucose levels of approximately 3 mmol during both fasting and postprandial periods requires only small glucose adjustment infusion in the diabetic pigs, as opposed to healthy ones. Using the described system, it would be possible to evaluate subclinical diabetes and control unstable diabetics with different therapeutic regimes.     

A Microcontroller Platform for the Rapid Prototyping of Functional Electrical Stimulation‐Based Gait Neuroprostheses

Functional electrical stimulation (FES) has been used over the last decades as a method to rehabilitate lost motor functions of individuals with spinal cord injury, multiple sclerosis, and post‐stroke hemiparesis. Within this field, researchers in need of developing FES‐based control solutions for specific disabilities often have to choose between either the acquisition and integration of high‐performance industry‐level systems, which are rather expensive and hardly portable, or develop custom‐made portable solutions, which despite their lower cost, usually require expert‐level electronic skills. Here, a flexible low‐cost microcontroller‐based platform for rapid prototyping of FES neuroprostheses is presented, designed for reduced execution complexity, development time, and production cost. For this reason, the Arduino open‐source microcontroller platform was used, together with off‐the‐shelf components whenever possible. The developed system enables the rapid deployment of portable FES‐based gait neuroprostheses, being flexible enough to allow simple open‐loop strategies but also more complex closed‐loop solutions. The system is based on a modular architecture that allows the development of optimized solutions depending on the desired FES applications, even though the design and testing of the platform were focused toward drop foot correction. The flexibility of the system was demonstrated using two algorithms targeting drop foot condition within different experimental setups. Successful bench testing of the device in healthy subjects demonstrated these neuroprosthesis platform capabilities to correct drop foot.     

A Technique for Sequential Segmental Neuromuscular Stimulation with Closed Loop Feedback Control

In dynamic myoplasty, dysfunctional muscle is assisted or replaced with skeletal muscle from a donor site. Electrical stimulation is commonly used to train and animate the skeletal muscle to perform its new task. Due to simultaneous tetanic contractions of the entire myoplasty, muscles are deprived of perfusion and fatigue rapidly, causing long-term problems such as excessive scarring and muscle ischemia. Sequential stimulation contracts part of the muscle while other parts rest, thus significantly improving blood perfusion. However, the muscle still fatigues. In this article, we report a test of the feasibility of using closed-loop control to economize the contractions of the sequentially stimulated myoplasty. A simple stimulation algorithm was developed and tested on a sequentially stimulated neo-sphincter designed from a canine gracilis muscle. Pressure generated in the lumen of the myoplasty neo-sphincter was used as feedback to regulate the stimulation signal via three control parameters, thereby optimizing the performance of the myoplasty. Additionally, we investigated and compared the efficiency of amplitude and frequency modulation techniques. Closed-loop feedback enabled us to maintain target pressures within 10% deviation using amplitude modulation and optimized control parameters (correction frequency = 4 Hz, correction threshold = 4%, and transition time = 0.3 s). The large-scale stimulation/feedback setup was unfit for chronic experimentation, but can be used as a blueprint for a small-scale version to unveil the theoretical benefits of closed-loop control in chronic experimentation.     

Evaluation of a Novel Artificial Pancreas: Closed Loop Glycemic Control System With Continuous Blood Glucose Monitoring

A closed‐loop glycemic control system using an artificial pancreas has been applied with many clinical benefits in Japan since 1987. To update this system incorporating user‐friendly features, we developed a novel artificial pancreas (STG‐55). The purpose of this study was to evaluate STG‐55 for device usability, performance of blood glucose measurement, glycemic control characteristics in vivo in animal experiments, and evaluate its clinical feasibility. There are several features for usability improvement based on the design concepts, such as compactness, display monitor, batteries, guidance function, and reduction of the preparation time. All animal study data were compared with a clinically available artificial pancreas system in Japan (control device: STG‐22). We examined correlations of both blood glucose levels between two groups (STG‐55 vs. control) using Clarke's error grid analysis, and also compared mean glucose infusion rate (GIR) during glucose clamp. The results showed strong correlation in blood glucose concentrations (Pearson's product‐moment correlation coefficient: 0.97; n = 1636). Clarke's error grid analysis showed that 98.4% of the data fell in Zones A and B, which represent clinically accurate or benign errors, respectively. The difference in mean GIRs was less than 0.2 mg/kg/min, which was considered not significant. Clinical feasibility study demonstrated sufficient glycemic control maintaining target glucose range between 80 and 110 (mg/dL), and between 140 and 160 without any hypoglycemia. In conclusion, STG‐55 was a clinically acceptable artificial pancreas with improved interface and usability. A closed‐loop glycemic control system with STG‐55 would be a useful tool for surgical and critical patients in intensive care units, as well as diabetic patients.     

Strength Improvement of Knee Extensor Muscles in Patients with Chronic Heart Failure by Neuromuscular Electrical Stimulation

Patients with severe chronic heart failure (CHF) suffer from marked weakness of skeletal muscles. Neuromuscular electrical stimulation (NMES) proved to be an alternative to active strength training. The objective of this study was to test the feasibility and effectiveness of NMES in patients with chronic heart failure. Seven patients (56.0 +/- 5.0 years, CHF for 20 +/- 4 months, left ventricular ejection fraction 20.1 +/- 10.0%) finished an 8 week course of NMES of the knee extensor muscles. The stimulator delivered biphasic, symmetric, constant voltage impulses of 0.7 ms pulse width with a frequency of 50 Hz, 2 s on and 6 s off. No adverse effects occurred. After the stimulation period, the isokinetic peak torque of the knee extensor muscles increased by 13% from 101.0 +/- 8.7 Nm to 113.5 +/- 7.2 Nm (p = 0.004). The maximal isometric strength increased by 20% from 294.3 +/- 19.6 N to 354.14 +/- 15.7 N (p = 0.04). This increased muscle strength could be maintained in a 20 min fatigue test indicating decreased muscle fatigue. These results demonstrate that NMES of skeletal muscles in patients with severe chronic heart failure is a promising method for strength training in this group of patients.     

A Custom Designed Chip to Control an Implantable Stimulator and Telemetry System for Control of Paralyzed Muscles

A custom designed chip has been developed for the control of paralyzed muscles. The system is capable of fulfilling the stimulus and telemetry needs of advanced functional neuromuscular stimulation (FNS) applications requiring multiple channels of stimulation and multiple channels for sensor or biopotential sensing. An inductive radiofrequency link provides power to the implant device as well as 2 way transcutaneous communication. An application specific integrated circuit (ASIC) decodes the commands and provides functional control within the implant, and modular circuitry provides specific implant functions. The ASIC chip provides up to 32 independent channels of stimulation with independent control of stimulus pulse duration, pulse amplitude, interphase delay, recharge phase duration, and pulse interval. It can also control up to 8 independent back telemetry analog channels with independent control of sampling rate and pulse powering parameters (amplitude and duration). The mixed analog digital chip has been fabricated in 1.2 microm n-well CMOS technology.     

Botulinum Toxin,Physical and Occupational Therapy,and Neuromuscular Electrical Stimulation to Treat Spastic Upper Limb of Children With Cerebral Palsy: A Pilot Study

Spasticity has been successfully managed with different treatment modalities or combinations. No information is available on the effectiveness or individual contribution of botulinum toxin type A (BTA) combined with physical and occupational therapy and neuromuscular electrical stimulation to treat spastic upper limb. The purpose of this study was to assess the effects of such treatment and to inform sample‐size calculations for a randomized controlled trial. BTA was injected into spastic upper limb muscles of 10 children. They received 10 sessions of physical and occupational therapy followed by 10 sessions of neuromuscular electrical stimulation on the wrist extensors (antagonist muscles). Degree of spasticity using the Modified Ashworth scale, active range of motion, and manual function with the Jebsen hand test, were assessed. Meaningful improvement was observed in hand function posttreatment (P = 0.03). Median spasticity showed a reduction trend and median amplitude of wrist range of motion registered an increase; however, neither of these were significant (P > 0.05). There is evidence of a beneficial effect of the combined treatment. Adequate information has been obtained on main outcome‐measurement variability for calculating sample size for a subsequent study to quantify the treatment effect precisely.     

Neuromuscular Electrical Stimulation Training Increases Intermuscular Fascial Length but Not Tendon Cross-Sectional Area After Spinal Cord Injury

Objective:

To determine the effects of 12 weeks of neuromuscular electrical stimulation (NMES) training with ankle weights on intermuscular fascial length and patellar tendon cross-sectional area (CSA) in persons with spinal cord injury (SCI).

Methods:

This study was a pre-post intervention. Seven men with motor complete SCI were randomly assigned to a resistance training plus diet (RT + diet) group (n = 4) or a diet control group (n = 3). Participants in the RT + diet group were enrolled in a 12-week leg extension weight-lifting program via surface NMES of the knee extensor muscle group. The length of mid-thigh intermuscular fascia and the patellar tendon CSA were measured using MRI.

Results:

In the RT + diet group, a nonsignificant 8% increase in the CSA of the patellar tendon (P = .14) was noted. The length of the mid-thigh intermuscular fascia increased by 19% and 23% in the right (P = .029) and left (P = .015) legs, respectively, with no changes in the diet control group. Positive relationships were noted between skeletal muscle CSAs of the whole thigh (r = 0.77, P = .041) and knee extensors (r = 0.76, P = .048) and intermuscular fascial length.

Conclusion:

The preliminary results suggest that noncontractile connective tissue structures of the knee extensors respond differently to NMES training after SCI. Skeletal muscle hypertrophy is associated with an increase in the intermuscular fascial length.     

Novel Neuromuscular Electrical Stimulation System for Treatment of Dysphagia after Brain Injury

The purpose of this study was to compare the effects of a novel neuromuscular electrical stimulation (NMES) to the effects of conventional treatment in patients with dysphagia after brain injury. In total, 26 patients were non-randomly divided into an experimental group (n = 12) and a control group (n = 14). The experimental group received NMES intervention followed by conventional treatment, including thermal-tactile stimulation with intensive repetition of a dry-swallow task. The control group received conventional treatment without NMES. NMES at a fixed pulse duration of 50 μs and a frequency of 50 Hz was delivered over the skin areas above the motor point of the target muscles, i.e., the bilateral geniohyoid, mylohyoid/anterior belly of the digastric, and thyrohyoid muscles, using a high-voltage pulsed-current device. The two groups received 40-min treatments once a day, 5 days per week, for 8 weeks. Outcome, assessed before and 8 weeks after treatment, was evaluated with regard to the videofluoroscopic dysphagia scale (VDS), the anterior and superior displacement of the hyoid bone and larynx, and the functional oral intake scale. Both groups exhibited improvement, but the experimental group exhibited more significant improvement in the displacement of the hyoid bone and larynx, VDS-total score, and VDS-pharyngeal score than the control group did. The results suggest that NMES combined with conventional treatment is superior to conventional treatment alone in patients with dysphagia following treatment for brain injury. Further investigations are necessary to examine the effects of NMES in patients with more varied types of diseases.     

Three Parameters Optimizing Closed-Loop Control in Sequential Segmental Neuromuscular Stimulation

In conventional dynamic myoplasties, the force generation is poorly controlled. This causes unnecessary fatigue of the transposed/transplanted electrically stimulated muscles and causes damage to the involved tissues. We introduced sequential segmental neuromuscular stimulation (SSNS) to reduce muscle fatigue by allowing part of the muscle to rest periodically while the other parts work. Despite this improvement, we hypothesize that fatigue could be further reduced in some applications of dynamic myoplasty if the muscles were made to contract according to need. The first necessary step is to gain appropriate control over the contractile activity of the dynamic myoplasty. Therefore, closed-loop control was tested on a sequentially stimulated neosphincter to strive for the best possible control over the amount of generated pressure. A selection of parameters was validated for optimizing control. We concluded that the frequency of corrections, the threshold for corrections, and the transition time are meaningful parameters in the controlling algorithm of the closed-loop control in a sequentially stimulated myoplasty.     

Use of Functional Electrical Stimulation in the Lower Extremities of Incomplete Spinal Cord Injured Patients

After a program of therapeutic electrical stimulation, 3 groups of incomplete spinal cord injured (SCI) patients were identified, those in whom an improvement of both voluntary and stimulated muscle force was observed, those with an increase in stimulation response only, and patients in whom no effect of electrical stimulation training could be recorded. As it is difficult to predict the outcome of the electrical stimulation rehabilitation process, a diagnostic procedure was developed to predict soon after accidents which incomplete SCI patients are candidates for permanent use of a functional electrical stimulation (FES) orthotic aid. The candidates for chronic use of FES are patients with weak ankle dorsiflexors and sufficiently strong knee extensors. These patients are equipped with a single channel peroneal stimulator augmenting dorsiflexion and knee and hip flexion in a total lower limb flexion response. By applying FES to the ankle plantar flexors, the swing phase of walking can be significantly shortened and faster walking obtained.     

Clinical elements for the neuromuscular stimulation and functional electrical stimulation protocols in the practice of neurorehabilitation

The physicians and their multidisciplinary teams involved in the clinical practice of neurological rehabilitation have more and more opportunities to apply neuromuscular stimulation (NMS) and functional electrical stimulation (FES) of peripheral nerves as a part of their daily practice. In this article, we outline clinical protocols of NMS and FES in the following clinical conditions of upper motor neuron dysfunction: to prevent consequences of disuse of the neuromuscular system of the upper motor neuron, to facilitate recovery processes of impaired upper motor neuron functions due to acute and/or subacute neurological conditions, to maintain or enhance the trophic state of the muscle, to modify altered control of muscle tone, to modify altered patterns of automatic and volitional functional movements, to enhance functional movement of the single joint muscle group within intact functional multijoint movement, and to modify altered neurocontrol of posture, locomotion, and skillful movements. We emphasize the importance of understanding the motor control alteration while developing clinical protocols and defining the goals. It is very important to be aware that similar clinical findings and due to the same cause can have different features of residual motor control, and therefore potentials for recovery or modification can be very different.     

Outcome of Functional Electrical Stimulation in the Rehabilitation of a Child with C-5 Tetraplegia

Abstract

Hand function was provided for a six-year-old child with C-5 American Spinal Injuries Association (ASIA) classification-A tetraplegia through a percutaneous intramuscular (IM) functional electrical stimulation (FES) system. In conjunction with implantation of 10 percutaneous IM electrodes for provision of grasp and release of her right hand, reconstructive surgery was performed to provide upper extremity positioning to optimize hand use. The subject participated in FES training over a nine-week period for approximately five hours weekly, with an additional five hours each week dedicated to exercise and conditioning of her arm muscles.

Physical and functional assessments included range of motion (ROM), manual muscle testing (MMT), activities of daily living (ADL) abilities and the Canadian Occupational Performance Measure (COPM), used to evaluate the effect of stimulated hand function and surgical reconstruction on functional ability. These were conducted prior to FES and surgery and repeated after rehabilitation training.

With rehabilitation and training, the child was able to control her FES system. Physical assessments revealed increased strength of both shoulders and more useful range of arm movement. Functional assessments show that the FES system enabled her to perform age-appropriate ADL that previously were achievable only with physical assistance. Her overall level of independence in ADL ability increased, as (lit) self-rated levels of satisfaction and performance on chosen activities. Positive gains demonstrated here suggest the need for further studies of FES systems in young children with SCI. () Spin.il Cord Med 1999;22:107–113)     

小低频联合手法按摩在产后妊娠纹修复中的应用

分析在产后妊娠纹修复中应用低频神经肌肉电刺激联合手法按摩的效果。方法 选取2022年 1月-2023年2月于黄骅市中医医院行妊娠纹修复的60例患者为研究对象,按随机数字表法分为对照组和观 察组,各30例。对照组采用单纯手法按摩修复,观察组采用低频神经肌肉电刺激联合手法按摩修复,比较 两组修复效果、腹部美观度、不良反应发生情况及复发情况。结果 观察组修复总有效率为96.67%,高于 对照组的73.33%（P＜0.05）;观察组治疗后腹部美观度评分低于对照组（P ＜0.05）;两组治疗后3、6个月 复发率比较,差异无统计学意义（P ＞0.05）;两组不良反应发生率比较,差异无统计学意义（P ＞0.05）。 结论 在产后妊娠纹修复中应用低频神经肌肉电刺激联合手法按摩的效果良好,能有效提升修复效果,改 善腹部美观度,且复发率及不良反应发生率均较低,应用有效性和安全性确切。     

Development of a Closed Air Loop Electropneumatic Actuator for Driving a Pneumatic Blood Pump

In this study, we developed a small pneumatic actuator that can be used as an extracorporeal biventricular assist device. It incorporated a bellows-transforming mechanism to generate blood-pumping pressure. The cylindrical unit is 88 ± 0.1 mm high, has a diameter of 150 ±  0.1 mm, and weighs 2.4 ± 0.01 kg. In vitro, maximal outflow at the highest pumping rate (PR) exceeded 8 L/min when two 55 mL blood sacs were used under an afterload pressure of 100 mm Hg. At a pumping rate of 100 beats per minute (bpm), maximal hydraulic efficiency was 9.34% when the unit supported a single ventricle and 13.8% when it supported both ventricles. Moreover, pneumatic efficiencies of the actuator were 17.3% and 33.1% for LVAD and BVAD applications, respectively. The energy equivalent pressure was 62.78∼208.10 mm Hg at a PR of 60∼100 bpm, and the maximal value of dP/dt during systole was 1269 mm Hg/s at a PR of 60 bpm and 979 mm Hg/s at a PR of 100 bpm. When the unit was applied to 15 calves, it stably pumped 3∼4 L/min of blood at 60 bpm, and no mechanical malfunction was experienced over 125 days of operation. We conclude that the presently developed pneumatic actuator can be utilized as an extracorporeal biventricular assist device.     

Evaluation of the Efficacy and Robustness of a Second Generation Implantable Stimulator in a Patient With Hemiplegia During 20 Years of Functional Electrical Stimulation of the Common Peroneal Nerve

We evaluated the efficacy and robustness of a second generation implantable stimulator for correcting drop foot (DF) in a patient with left‐sided hemiplegia over 20 years of functional electrical stimulation (FES) of the common peroneal nerve (CPN). Dorsal flexion and eversion of the affected foot was partially restored by FES of the superficial region of the CPN innervating mostly the tibialis anterior (TA) and partly peroneus longus (PL) and peroneus brevis (PB) muscles. The reasons for implant failure during the long‐term follow‐up assessment were analyzed and resolving procedures were identified. The stimulator had an average failure rate of once every three years, due to repetitive mechanical load on the lead wires of its internal and/or external unit, and had to be serviced once per year to replace the heel switch integrated into the shoe sole. FES‐associated mechanical trauma to the CPN elicited a thickening of the connective tissue around the CPN and a slightly compromised conduction velocity of the CPN. FES of the CPN, with the second generation implantable stimulator, improved gait parameters of the affected leg during the 20 years period. Long‐term, daily FES enables a functional and reliable recruitment of nerve fibers, thus providing a sufficient dorsal flexion and optimal eversion of the affected foot to sustain unassisted, almost normal gait. Therefore, the presented implant is suitable for very long‐term FES of the CPN.     

经皮穴位电刺激复合药物全麻行控制性降压的控压效应分析

目的:探讨经皮穴位电刺激复合药物全麻行控制性降压至不同平均动脉血压(MAP)水平的控压效应变化.方法:54只雄性比格犬随机分为9组,每组6只,控压组动物均以异氟烷复合硝普钠行控制性降压术,单纯全麻组不行控制性降压,实验组采用经皮穴位电刺激(TEAS)干预处理.结果:在行控制性降压至基础MAP60%水平时,在血压回升阶段,实验组动物MAP的回升速度和幅度均高于同水平对照组,在回升30 min时基本恢复至基础水平,对照组仍显著低于其基础水平(P<0.05);与单纯全麻组相比,50%基础MAP对照组、40%基础MAP对照组苏醒时间明显增加(P<0.05);60%基础MAP、40%基础MAP实验组被动放血量明显减少(P<0.05),50%基础MAP、30%基础MAP实验组术中自然失血量明显减少(P<0.05).结论:TEAS能加快机体MAP的恢复,并有效缩短了实验动物的苏醒时间;同时能不同程度的减少术中失血量,从而对机体起到保护作用.