Neuromuscular electrical stimulation for preventing skeletal-muscle weakness and wasting in critically ill patients: a systematic review

Using Physiological Markers to Assess Comfort during Neuromuscular Electrical Stimulation Induced Muscle Contraction in a Virtually Guided Environment: Pilot Study for a Path toward Combating ICU-Acquired Weakness

We assessed the feasibility of implementing a virtually guided Neuromuscular Electrical Stimulation (NMES) protocol over the tibialis anterior (TA) muscle while collecting heart rate (HR), Numeric Pain Rating Scale (NPRS), and quality of contraction (QoC) data. We investigated if HR, NPRS, and QoC differ ON and OFF the TA motor point and explored potential relationships between heart rate variability (HRV) and the NPRS. Twelve healthy adults participated in this cross-sectional study. Three NMES trials were delivered ON and OFF the TA motor point. HR, QoC, and NPRS data were collected. There was no significant difference in HRV ON and OFF the motor point (p > 0.05). The NPRS was significantly greater OFF the motor point (p < 0.05). The QoC was significantly different between motor point configurations (p < 0.05). There was no correlation between the NPRS and HRV (p > 0.05, r = -0.129). We recommend non-electrical methods of measuring muscle activity for future studies. The NPRS and QoC can be administered virtually. Time-domain HRV measures could increase the validity of the protocol. The variables should be explored further virtually to enhance the protocol before eventual ICU studies.

The effect of neuromuscular electrical stimulation applied at different muscle lengths on muscle architecture and sarcomere morphology in rats

Neuromuscular electrical stimulation (NMES) is often used to increase muscle strength and functionality. Muscle architecture is important for the skeletal muscle functionality. The aim of this study was to investigate the effects of NMES applied at different muscle lengths on skeletal muscle architecture. Twenty-four rats were randomly assigned to four groups (two NMES groups and two control groups). NMES was applied on the extensor digitorum longus muscle at long muscle length, which is the longest and stretched position of the muscle at 170° plantar flexion, and at medium muscle length, which is the length of the muscle at 90° plantar flexion. A control group was created for each NMES group. NMES was applied for 8 weeks, 10 min/day, 3 days/week. After 8 weeks, muscle samples were removed at the NMES intervention lengths and examined macroscopically, and microscopically using a transmission electron microscope and streo-microscope. Muscle damage, and architectural properties of the muscle including pennation angle, fibre length, muscle length, muscle mass, physiological cross-sectional area, fibre length/muscle length, sarcomere length, sarcomere number were then evaluated. There was an increase in fibre length and sarcomere number, and a decrease in pennation angle at both lengths. In the long muscle length group, muscle length was increased, but widespread muscle damage was observed. These results suggest that the intervention of NMES at long muscle length can increase the muscle length but also causes muscle damage. In addition, the greater longitudinal increase in muscle length may be a result of the continuous degeneration-regeneration cycle.

Clinical treatment for persistent inflammation, immunosuppression and catabolism syndrome in patients with severe acute pancreatitis (Review)

Severe acute pancreatitis (SAP) is a severe disease with a high prevalence and a 3-15% mortality worldwide, and premature activation of zymogen for any reason is the initial factor for the onset of SAP. Gallstone disease and heavy alcohol consumption are the two most common etiologies of SAP. Persistent inflammation, immunosuppression and catabolism syndrome (PICS) is a life-threatening illness, and there are no effective treatments. The relapse state of PICS mainly leads to high mortality due to septic shock or severe trauma, both of which are dangerous and challenging conditions for clinicians. Thus, it is important for medical staff to identify patients at high risk of PICS and to master the prevention and treatment of PICS in patients with SAP. The present review aims to increase the understanding of the pathogenesis of PICS, produce evidence for PICS diagnosis and highlight clinical treatment for PICS in patients with SAP. With this information, clinical workers could implement standardized and integrated measures at an early stage of SAP to stop its progression to PICS.

Effects of two different paradigms of electrical stimulation exercise on cardio-metabolic risk factors after spinal cord injury. A randomized clinical trial

Objective

To examine the combined effects of neuromuscular electrical stimulation-resistance training (NMES-RT) and functional electrical stimulation-lower extremity cycling (FES-LEC) compared to passive movement training (PMT) and FES-LEC in adults with SCI on (1) oxygen uptake (VO2), insulin sensitivity and glucose disposal in adults with SCI; (2) Metabolic and inflammatory biomarkers; (3) skeletal muscle, intramuscular fat (IMF) and visceral adipose tissue (VAT) cross-sectional areas (CSAs).

Materials and methods

Thirty-three participants with chronic SCI (AIS A-C) were randomized to 24 weeks of NMES-RT + FES or PMT + FES. The NMES-RT + FES group underwent 12 weeks of evoked surface NMES-RT using ankle weights followed by an additional 12 weeks of progressive FES-LEC. The control group, PMT + FES performed 12 weeks of passive leg extension movements followed by an additional 12 weeks of FES-LEC. Measurements were performed at baseline (BL; week 0), post-intervention 1 (P1; week 13) and post-intervention 2 (P2; week 25) and included FES-VO2 measurements, insulin sensitivity and glucose effectiveness using the intravenous glucose tolerance test; anthropometrics and whole and regional body composition assessment using dual energy x-ray absorptiometry (DXA) and magnetic resonance imaging to measure muscle, IMF and VAT CSAs.

Results

Twenty-seven participants completed both phases of the study. NMES-RT + FES group showed a trend of a greater VO2 peak in P1 [p = 0.08; but not in P2 (p = 0.25)] compared to PMT + FES. There was a time effect of both groups in leg VO2 peak. Neither intervention elicited significant changes in insulin, glucose, or inflammatory biomarkers. There were modest changes in leg lean mass following PMT + FES group. Robust hypertrophy of whole thigh muscle CSA, absolute thigh muscle CSA and knee extensor CSA were noted in the NMES-RT + FES group compared to PMT + FES at P1. PMT + FES resulted in muscle hypertrophy at P2. NMES-RT + FES resulted in a decrease in total VAT CSA at P1.

Conclusion

NMES-RT yielded a greater peak leg VO2 and decrease in total VAT compared to PMT. The addition of 12 weeks of FES-LEC in both groups modestly impacted leg VO2 peak. The addition of FES-LEC to NMES-RT did not yield additional increases in muscle CSA, suggesting a ceiling effect on signaling pathways following NMES-RT.

Clinical trial registration

identifier NCT02660073.

Early Neuromuscular Electrical Stimulation Preserves Muscle Size and Quality and Maintains Systemic Levels of Signaling Mediators of Muscle Growth and Inflammation in Patients with Traumatic Brain Injury: A Randomized Clinical Trial

Objective

To investigate the effects of an early neuromuscular electrical stimulation (NMES) protocol on muscle quality and size as well as signaling mediators of muscle growth and systemic inflammation in patients with traumatic brain injury (TBI).

Design

Two-arm, single-blinded, parallel-group, randomized, controlled trial with a blinded assessment. Setting. Trauma intensive care unit at a university hospital. Participants. Forty consecutive patients on mechanical ventilation (MV) secondary to TBI were prospectively recruited within the first 24 hours following admission. Interventions. The intervention group (NMES; n = 20) received a daily session of NMES on the rectus femoris muscle for five consecutive days (55 min/each session). The control group (n = 20) received usual care. Main Outcome Measures. Muscle echogenicity and thickness were evaluated by ultrasonography. A daily blood sample was collected to assess circulating levels of insulin-like growth factor I (IGF-I), inflammatory cytokines, and matrix metalloproteinases (MMP).

Results

Both groups were similar at baseline. A smaller change in muscle echogenicity and thickness (difference between Day 1 and Day 7) was found in the control group compared to the NMES group (29.9 ± 2.1 vs. 3.0 ± 1.2, p < 0.001; -0.79 ± 0.12 vs. -0.01 ± 0.06, p < 0.001, respectively). Circulating levels of IGF-I, pro-inflammatory cytokines (IFN-y), and MMP were similar between groups.

Conclusion

An early NMES protocol can preserve muscle size and quality and maintain systemic levels of signaling mediators of muscle growth and inflammation in patients with TBI. This trial is registered with https://www.ensaiosclinicos.gov.br under number RBR-2db.

Functional electrical stimulation therapy for upper extremity rehabilitation following spinal cord injury: a pilot study

STUDY DESIGN

Pilot study.

OBJECTIVES

To examine if functional electrical stimulation therapy (FEST) improves neuromuscular factors underlying upper limb function in individuals with SCI.

SETTING

A tertiary spinal cord rehabilitation center specialized in spinal cord injury care in Canada.

METHODS

We examined 29 muscles from 4 individuals living with chronic, cervical, and incomplete SCI. The analysis was focused on the changes in muscle activation, as well as on how the treatment could change the ability to control a given muscle or on how multiple muscles would be coordinated during volitional efforts.

RESULTS

There was evidence of gains in muscle strength, activation, and median frequency after the FEST. Gains in muscle activation indicated the activation of a greater number of motor units and gains in muscle median frequency the involvement of higher threshold, faster motor units. In some individuals, these changes were smaller but accompanied by increased control over muscle contraction, evident in a greater ability to sustain a volitional contraction, reduce the co-contraction of antagonist muscles, and provide cortical drive.

CONCLUSIONS

FEST increases muscle strength and activation. Enhanced control of muscle contraction, reduced co-contraction of antagonist muscles, and a greater presence of cortical drive were some of the findings supporting the effects of FEST at the sensory-motor integration level.

Elderly Patients and Management in Intensive Care Units (ICU): Clinical Challenges

There is a growing population of older adults requiring admission to the intensive care unit (ICU). This population outpaces the ability of clinicians with geriatric training to assist in their management. Specific training and education for intensivists in the care of older patients is valuable to help understand and inform clinical care, as physiologic changes of aging affect each organ system. This review highlights some of these aging processes and discusses clinical implications in the vulnerable older population. Other considerations when caring for these older patients in the ICU include functional outcomes and morbidity, as opposed to merely a focus on mortality. An overall holistic approach incorporating physiology of aging, applying current evidence, and including the patient and their family in care should be used when caring for older adults in the ICU.

The effects of external diaphragmatic pacing on diaphragm function and weaning outcomes of critically ill patients with mechanical ventilation: a prospective randomized study

BACKGROUND

Diaphragmatic pacing can improve diaphragm function, which is beneficial for the prognosis of patients treated with prolonged mechanical ventilation (MV). While most previous studies have focused on the role of implanted diaphragm pacing (IDP), our study is the first to examine the effects of external diaphragmatic pacing (EDP) in mechanically ventilated patients. Specifically, the effect of EDP on diaphragm function, the success rate of weaning, the duration of MV (DMV), and the intensive care unit (ICU) length of stay (ILOS) were assessed.

METHODS

From September 2019 to December 2020, a total of 51 mechanically ventilated patients in the ICU of the Sun Yat-sen Memorial Hospital, Sun Yat-sen University were enrolled and randomly divided into an EDP group of 27 patients and a control group of 24 patients. The control group received routine treatment, and the EDP group received EDP treatment in addition to routine treatment. The diaphragm excursion (DE), diaphragm thickening fraction (DTF), DMV, ILOS, and average survival time were recorded to evaluate efficacy.

RESULTS

Patients treated with EDP had increased DE [exp(B) =1.86, 95% CI: 1.39 to 2.50, P<0.001] and DTF [exp(B) =1.35, 95% CI: 1.05 to 1.76, P=0.022], shortened weaning time (P=0.026) and prolonged average survival time (P<0.001) compared to patients who did not receive EDP therapy. Especially in cases with difficult weaning, the improvement of DE and DTF in the EDP treatment group was more obvious than that in the control group (P=0.013 and P=0.032). Moreover, the DTF upon attempted spontaneous breathing trial (SBT) was negatively correlated with the fraction of inspired oxygen (FiO2) [r=-0.54; 95% confidence interval (CI): -0.77 to -0.19; P=0.004], the arterial partial pressure of oxygen (PaO2) (r=-0.58; 95% CI: -0.79 to -0.25; P=0.001), the PaO2/FiO2 ratio (r=-0.52; 95% CI: -0.75 to -0.16; P=0.006), and the serum lactate concentration (Lac) (r=-0.39; 95% CI: -0.68 to 0.003; P=0.046).

CONCLUSIONS

EDP treatment can effectively reduce the DMV and prolong the average survival time of mechanically ventilated patients.

TRIAL REGISTRATION

Chinese Clinical Trial Registry ChiCTR1900024096.

Assessment of neuromuscular electrical stimulation in critically ill patients: physical therapists’ knowledge and barriers to its use

ABSTRACT Transcutaneous neuromuscular electrical stimulation (NMES) is considered an important tool to prevent muscle mass and strength loss in patients admitted to intensive care units (ICU). This study aimed to evaluate physical therapists’ profile and knowledge of NMES and identify the main barriers to its use in ICUs. This observational cross-sectional study was conducted via a structured questionnaire created by the authors. It consisted of 12 objective questions to analyze physical therapists’ knowledge of NMES use in critically ill patients. Physical therapists were invited to participate in this study during an international symposium on NMES. In total, 56 physical therapists, with a mean age of 33.5±7.2 years and working an average of 9.7±7 years after graduation, completed the survey. Overall, 34 respondents worked in ICUs, of which only four (12%) reported regular NMES use in their ICUs. We found a low average of correct answers to our questionnaire (25%; 3/12). The main barriers reported to using NMES in ICUs were lack of knowledge (28; 50%) and equipment (24; 43%). The number of correct answers expert and non-expert physical therapists was not statistically significant (p=0.68). Thus, we observed participants’ poor knowledge of NMES use in critically ill patients. Respondents showed that NMES has been underused in their ICUs. Lack of knowledge and equipment seems to be the main barriers for the use of NMES in ICUs.

Molecular Mechanisms Underlying Intensive Care Unit-Acquired Weakness and Sarcopenia

Skeletal muscle is a highly adaptable organ, and its amount declines under catabolic conditions such as critical illness. Aging is accompanied by a gradual loss of muscle, especially when physical activity decreases. Intensive care unit-acquired weakness is a common and highly serious neuromuscular complication in critically ill patients. It is a consequence of critical illness and is characterized by a systemic inflammatory response, leading to metabolic stress, that causes the development of multiple organ dysfunction. Muscle dysfunction is an important component of this syndrome, and the degree of catabolism corresponds to the severity of the condition. The population of critically ill is aging; thus, we face another negative effect-sarcopenia-the age-related decline of skeletal muscle mass and function. Low-grade inflammation gradually accumulates over time, inhibits proteosynthesis, worsens anabolic resistance, and increases insulin resistance. The cumulative consequence is a gradual decline in muscle recovery and muscle mass. The clinical manifestation for both of the above conditions is skeletal muscle weakness, with macromolecular damage, and a common mechanism-mitochondrial dysfunction. In this review, we compare the molecular mechanisms underlying the two types of muscle atrophy, and address questions regarding possible shared molecular mechanisms, and whether critical illness accelerates the aging process.

Safety and Feasibility Assessment of Repetitive Vascular Occlusion Stimulus (RVOS) Application to Multi-Organ Failure Critically Ill Patients: A Pilot Randomised Controlled Trial

Muscle wasting is implicated in the pathogenesis of intensive care unit acquired weakness (ICU-AW), affecting 40% of patients and causing long-term physical disability. A repetitive vascular occlusion stimulus (RVOS) limits muscle atrophy in healthy and orthopaedic subjects, thus, we explored its application to ICU patients. Adult multi-organ failure patients received standard care +/- twice daily RVOS {4 cycles of 5 min tourniquet inflation to 50 mmHg supra-systolic blood pressure, and 5 min complete deflation} for 10 days. Serious adverse events (SAEs), tolerability, feasibility, acceptability, and exploratory outcomes of the rectus femoris cross-sectional area (RFCSA), echogenicity, clinical outcomes, and blood biomarkers were assessed. Only 12 of the intended 32 participants were recruited. RVOS sessions (76.1%) were delivered to five participants and two could not tolerate it. No SAEs occurred; 75% of participants and 82% of clinical staff strongly agreed or agreed that RVOS is an acceptable treatment. RFCSA fell significantly and echogenicity increased in controls (n = 5) and intervention subjects (n = 4). The intervention group was associated with less frequent acute kidney injury (AKI), a greater decrease in the total sequential organ failure assessment score (SOFA) score, and increased insulin-like growth factor-1 (IGF-1), and reduced syndecan-1, interleukin-4 (IL-4) and Tumor necrosis factor receptor type II (TNF-RII) levels. RVOS application appears safe and acceptable, but protocol modifications are required to improve tolerability and recruitment. There were signals of possible clinical benefit relating to RVOS application.

A randomized controlled clinical trial of the effects of range of motion exercises and massage on muscle strength in critically ill patients

Background

Atrophy and muscle weakness is a common problem in critically ill patients admitted to the intensive care unit (ICU). Muscle weakness in severe cases can lead to tetraplegia, reduced or lost tendon reflexes, delayed weaning from mechanical ventilation, physical disability, and increased mortality. The aim of this study was to compare the effects of range of motion exercises (ROM) and massage on muscle strength of the patients admitted to ICUs.

Methods

This study was a single-blinded randomized controlled trial conducted in ICUs of Afzalipour hospital in Kerman, southeastern Iran. Ninety conscious ICU patients were randomly divided into three groups (massage, ROM exercises and control). The researcher/co-researcher massaged or did ROM exercises on the patients’ extremities once a day for seven consecutive days. Using a hand-held dynamometer, the co-researcher, rated the muscle strength before, on the fourth and seventh days of intervention at 8 p.m.

Results

The mean muscles strength of the right arm in the ROM exercise and massage groups increased by 0.63 kg, and 0.29 kg, respectively after the intervention compared with before the intervention. The muscle strength of the right arm in the control group reduced by 0.55 kg. The mean muscles strength of the left arm in the ROM exercise and massage groups increased by 0.61 kg and 0.28 kg after the intervention, respectively while it reduced by 0.56 kg in the control group. The mean muscles strength of the right leg in the ROM exercise and massage groups increased by 0.53 kg and 0.27 kg after the intervention compared with before the intervention while it reduced by 0.70 kg in the control group. The mean muscles strength of the left leg in the ROM exercise and massage groups increased by 0.54 kg and 0.26 kg after the intervention compared with before the intervention while it reduced by 0.71 kg in the control group.

Conclusion

The results of the present study showed that ROM exercises and massage were effective interventions in increasing muscle strength of the critically ill patients admitted to intensive care units.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13102-022-00489-z.

Early Neuromuscular Electrical Stimulation in Addition to Early Mobilization Improves Functional Status and Decreases Hospitalization Days of Critically Ill Patients

OBJECTIVES

To evaluate the impact of the additional use of early neuromuscular electrical stimulation (NMES) on an early mobilization (EM) protocol.

DESIGN

Randomized controlled trial.

SETTING

ICU of the Clinical Hospital of Ribeirão Preto, University of São Paulo, Brazil.

PATIENTS

One hundred and thirty-nine consecutive mechanically ventilated patients were included in the first 48 hours of ICU admission.

INTERVENTIONS

The patients were divided into two groups: EM and EM+NMES. Both groups received EM daily. In the EM+NMES group, patients additionally received NMES 5 days a week, for 60 minutes, starting in the first 48 hours of ICU admission until ICU discharge.

MEASUREMENTS AND MAIN RESULTS

Functional status, muscle strength, ICU and hospital length of stay (LOS), frequency of delirium, days on mechanical ventilation, mortality, and quality of life were assessed. Patients in the EM+NMES group presented a significant higher score of functional status measured by the Functional Status Score for the ICU scale when compared with the EM group in the first day awake: 22 (15-26) versus 12 (8-22) (p = 0.019); at ICU discharge: 28 (21-33) versus 18 (11-26) (p = 0.004); and hospital discharge: 33 (27-35) versus 25 (17-33) (p = 0.014), respectively. They also had better functional status measured by the Physical Function Test in the ICU scale, took less days to stand up during the ICU stay, and had a significant shorter hospital LOS, lower frequency of ICU-acquired weakness, and better global muscle strength.

CONCLUSIONS

The additional application of early NMES promoted better functional status outcomes on the first day awake and at ICU and hospital discharge. The patients in the EM+NMES group also took fewer days to stand up and had shorter hospital LOS, lower frequency of ICU-acquired weakness, and better muscle strength. Future studies are still necessary to clarify the effects of therapies associated with EM, especially to assess long-term outcomes.

Effect of neuromuscular electrical stimulation on functional exercise capacity in patients undergoing cardiac surgery: A randomized clinical trial

OBJECTIVE

To evaluate the effects of neuromuscular electrical stimulation on functional capacity of patients in the immediate postoperative period of cardiac surgery.

DESIGN

A prospective, randomized controlled trial.

SETTING

A cardiac surgery specialist hospital in Aracaju, Sergipe, Brazil. Subjects: Patients in the postoperative period of cardiac surgery.

INTERVENTION

The control group received the conventional physiotherapy and the intervention group received neuromuscular electrical stimulation of the rectus femoris and gastrocnemius muscles bilaterally, applied for 60 min, twice a day for up to 10 sessions per patient, in the immediate postoperative period until postoperative day 5.

MAIN MEASURES

The primary outcome was the distance walked, which was evaluated using the 6-min walk test on postoperative day 5. Secondary outcomes were gait speed, lactate levels, muscle strength, electromyographic activity of the rectus femoris and Functional Independence Measure, some of them evaluated on preoperative and postoperative period.

RESULTS

Of 132 eligible patients, 88 patients were included and randomly allocated in two groups, and 45 patients were included in the analysis. No significant difference was found on the distance walked (p = 0.650) between patients allocated in intervention group (239.06 ± 88.55) and control group (254.43 ± 116.67) as well as gait speed (p = 0.363), lactate levels (p = 0.302), knee extensor strength (p = 0.117), handgrip strength (p = 0.882), global muscle strength (p = 0.104), electromyographic activity (p = 0.179) and Functional Independence Measure (p = 0.059).

CONCLUSIONS

Although the effects are still uncertain, the use of neuromuscular electrical stimulation carried out in five days didn't present any benefit on functional capacity of patients in the immediate postoperative period of cardiac surgery.

The effect of passive mobilization associated with blood flow restriction and combined with electrical stimulation on cardiorespiratory safety, neuromuscular adaptations, physical function, and quality of life in comatose patients in an ICU: a randomized controlled clinical trial

Background

Intensive care unit-acquired atrophy and weakness are associated with high mortality, a reduction in physical function, and quality of life. Passive mobilization (PM) and neuromuscular electrical stimulation were applied in comatose patients; however, evidence is inconclusive regarding atrophy and weakness prevention. Blood flow restriction (BFR) associated with PM (BFRp) or with electrical stimulation (BFRpE) was able to reduce atrophy and increase muscle mass in spinal cord-injured patients, respectively. Bulky venous return occurs after releasing BFR, which can cause unknown repercussions on the cardiovascular system. Hence, the aim of this study was to investigate the effect of BFRp and BFRpE on cardiovascular safety and applicability, neuromuscular adaptations, physical function, and quality of life in comatose patients in intensive care units (ICUs).

Methods

Thirty-nine patients will be assessed at baseline (T0–18 h of coma) and randomly assigned to the PM (control group), BFRp, or BFRpE groups. The training protocol will be applied in both legs alternately, twice a day with a 4-h interval until coma awake, death, or ICU discharge. Cardiovascular safety and applicability will be evaluated at the first training session (T1). At T0 and 12 h after the last session (T2), muscle thickness and quality will be assessed. Global muscle strength and physical function will be assessed 12 h after T2 and ICU and hospital discharge for those who wake up from coma. Six and 12 months after hospital discharge, physical function and quality of life will be re-assessed.

Discussion

In view of applicability, the data will be used to inform the design and sample size of a prospective trial to clarify the effect of BFRpE on preventing muscle atrophy and weakness and to exert the greatest beneficial effects on physical function and quality of life compared to BFRp in comatose patients in the ICU.

Trial registration

Universal Trial Number (UTN) Registry UTN U1111-1241-4344. Retrospectively registered on 2 October 2019. Brazilian Clinical Trials Registry (ReBec) RBR-2qpyxf. Retrospectively registered on 21 January 2020, http://ensaiosclinicos.gov.br/rg/RBR-2qpyxf/

Supplementary Information

The online version contains supplementary material available at 10.1186/s13063-021-05916-z.

Multifocal Noninvasive Magnetic Stimulation of the Primary Motor Cortex in Type 1 Myotonic Dystrophy -A Proof of Concept Pilot Study

BACKGROUND

Repeated neuromuscular electrical stimulation in type 1 Myotonic Dystrophy (DM1) has previously been shown to cause an increase in strength and a decrease in hyperexcitability of the tibialis anterior muscle.

OBJECTIVE

In this proof-of-principle study our objective was to test the hypothesis that noninvasive repetitive transcranial magnetic stimulation of the primary motor cortex (M1) with a new portable wearable multifocal stimulator causes improvement in muscle function in DM1 patients.

METHODS

We performed repetitive stimulation of M1, localized by magnetic resonance imaging, with a newly developed Transcranial Rotating Permanent Magnet Stimulator (TRPMS). Using a randomized within-patient placebo-controlled double-blind TRPMS protocol, we performed unilateral active stimulation along with contralateral sham stimulation every weekday for two weeks in 6 adults. Methods for evaluation of muscle function involved electromyography (EMG), hand dynamometry and clinical assessment using the Medical Research Council scale.

RESULTS

All participants tolerated the treatment well. While there were no significant changes clinically, EMG showed significant improvement in nerve stimulus-evoked compound muscle action potential amplitude of the first dorsal interosseous muscle and a similar but non-significant trend in the trapezius muscle, after a short exercise test, with active but not sham stimulation.

CONCLUSIONS

We conclude that two-week repeated multifocal cortical stimulation with a new wearable transcranial magnetic stimulator can be safely conducted in DM1 patients to investigate potential improvement of muscle strength and activity. The results obtained, if confirmed and extended by future safety and efficacy trials with larger patient samples, could offer a potential supportive TRPMS treatment in DM1.

Triboelectric Nanogenerators for Therapeutic Electrical Stimulation

Current solutions developed for the purpose of in and on body (IOB) electrical stimulation (ES) lack autonomous qualities necessary for comfortable, practical, and self-dependent use. Consequently, recent focus has been placed on developing self-powered IOB therapeutic devices capable of generating therapeutic ES for human use. With the recent invention of the triboelectric nanogenerator (TENG), harnessing passive human biomechanical energy to develop self-powered systems has allowed for the introduction of novel therapeutic ES solutions. TENGs are especially effective at providing ES for IOB therapeutic systems given their bioconformability, low cost, simple manufacturability, and self-powering capabilities. Due to the key role of naturally induced electrical signals in many physiological functions, TENG-induced ES holds promise to provide a novel paradigm in therapeutic interventions. The aim here is to detail research on IOB TENG devices applied for ES-based therapy in the fields of regenerative medicine, neurology, rehabilitation, and pharmaceutical engineering. Furthermore, considering TENG-produced ES can be measured for sensing applications, this technology is paving the way to provide a fully autonomous personalized healthcare system, capable of IOB energy generation, sensing, and therapeutic intervention. Considering these grounds, it seems highly relevant to review TENG-ES research and applications, as they could constitute the foundation and future of personalized healthcare.

Long-term effect of task-oriented functional electrical stimulation in chronic Guillain Barré syndrome-a single-subject study

OBJECTIVE

Functional electrical stimulation (FES) can enhance motor learning of hand fine motor skills in neurological diseases with upper motoneuron lesions. Nevertheless, FES is rarely applied in patients with chronic Guillan-Barré syndrome (GBS) with preserved deep tendon reflexes allowing for stimulation via nerve. This single case report documents the results of an FES-supported, task-oriented grasp training to regain hand closure and pinch grip.

STUDY DESIGN

Single-subject repeated measures study.

SETTING

International FES Centre®, Swiss Paraplegic Centre Nottwil.

METHODS

Three individually defined goals were formulated and scored by using the goal attainment scale. With a focus on these goals, FES was applied bilaterally to improve hand closure and pinch grip. Based on principles of motor learning FES was executed together with task-oriented movements. The hand closure distance (cm) between the tip of the middle finger and the palmar side of the hand was measured and the achievement of personal, predefined goals evaluated.

RESULTS

After 16 weeks of daily stimulation, hand closure could be voluntarily performed. Regained opposition of the thumb to the index finger enabled improved individually defined fine motor control. Restored function remained unchanged in the follow-up at 6 months without stimulation.

CONCLUSION

Improving fine motor skills in chronic GBS with intact deep tendon reflexes was possible utilizing FES combined with task-oriented grasp training. These improvements were maintained over time indicating the combination was effective in promoting functionally meaningful motor gains.

Static balance adaptations after neuromuscular electrical stimulation on quadriceps and lumbar paraspinal muscles in healthy elderly

Background

Strength training as neuromuscular electrical stimulation (NMES) is effective in counteracting age-related postural impairments in elderly. However, it remains unknown whether training different muscle groups would entail in different adaptations.

Aim

To evaluate the effect of NMES training on balance function in healthy inactive elderly, targeting paravertebral muscles, in addition to thigh muscles.

Methods

Eleven healthy elderly were trained with NMES for 8 week allocated to combined training (CT: quadriceps and lumbar paraspinal muscles) or to quadriceps training (QT), after completing lifestyle questionnaire and spine morphology measurements. Functional balance, static stabilometry, and isometric strength tests were assessed before and after the training period.

Results and conclusion

The CT group showed a greater improve in static balance control, i.e., reducing the CEA of the CoP displacement from 99 ± 38 to 76 ± 42 mm2 (Cohen’s d = 0.947). Benefits for improving static balance through CT might be due to NMES training, which increases spinal stabilization.

Blood Flow Restriction Combined with Electrical Stimulation Attenuates Thigh Muscle Disuse Atrophy

PURPOSE

This study aimed to investigate the effects of blood flow restriction (BFR) combined with electrical muscle stimulation (EMS) on skeletal muscle mass and strength during a period of limb disuse.

METHODS

Thirty healthy participants (22 ± 3 yr; 23 ± 3 kg·m-2) were randomly assigned to control (CON; n = 10), BFR alone (BFR; n = 10), or BFR combined with EMS (BFR + EMS; n = 10). All participants completed unloading of a single leg for 14 d, with no treatment (CON), or while treated with either BFR or BFR + EMS (twice daily, 5 d·wk-1). BFR treatment involved arterial three cycles of 5-min occlusion using suprasystolic pressure, each separated by 5 min of reperfusion. EMS (6 s on, 15 s off; 200 μs; 60 Hz; 15% maximal voluntary contraction [MVC]) was applied continuously throughout the three BFR cycles. Quadriceps muscle mass (whole-thigh lean mass via dual-energy x-ray absorptiometry and vastus lateralis [VL] muscle thickness via ultrasound) and strength (via knee extension MVC) were assessed before and after the 14-d unloading period.

RESULTS

After limb unloading, whole-thigh lean mass decreased in the control group (-4% ± 1%, P < 0.001) and BFR group (-3% ± 2%, P = 0.001), but not in the BFR + EMS group (-0.3% ± 3%, P = 0.8). VL muscle thickness decreased in the control group (-4% ± 4%, P = 0.005) and was trending toward a decrease in the BFR group (-8% ± 11%, P = 0.07) and increase in the BFR + EMS group (+5% ± 10%, P = 0.07). Knee extension MVC decreased over time (P < 0.005) in the control group (-18% ± 15%), BFR group (-10% ± 13%), and BFR + EMS group (-18% ± 15%), with no difference between groups (P > 0.5).

CONCLUSION

Unlike BFR performed in isolation, BFR + EMS represents an effective interventional strategy to attenuate the loss of muscle mass during limb disuse, but it does not demonstrate preservation of strength.

A systematic review of using electrical stimulation to improve clinical outcomes after hip fractures

BACKGROUND

Pain and muscles weakness often delays regaining independent mobility following hip fracture surgery. Electrical stimulation may relieve pain and improve muscle strength and function.

PURPOSE

To systematically review and evaluate available literature examining the effectiveness of using electrical stimulation to promote clinical outcomes after hip fractures.

METHODS

Two researchers independently searched MEDLINE, CINAHL, EMBASE, Web of Science, Cochrane Reviews, Physiotherapy Evidence Database, and PsycInfo from inception to July 1, 2018, with no restrictions. The quality and fidelity of the included interventions were assessed, and expert consultation was conducted to help explain the results.

RESULTS

We identified 432 records through database searching. Initial screening indicated 24 articles were appropriate for full-text review, and four articles met the inclusion criteria. In included studies, electrical stimulation (i.e. TENS) reduced pain (mean difference (MD) = 3.3 points on 10-point Visual Analogue Scale, p < .001), improved range of motion (ROM) (MD: 25.7°, p < .001), and accelerated functional recovery immediately after hip fracture (p < .001). Conflicting evidence existed when using neuromuscular electrical stimulation to improve muscle strength and other functional outcomes (e.g. mobility); however, nine experts advised that longer-term interventions might be necessary to achieve significant improvment in muscle strength.

CONCLUSION

Available evidence, albeit limited, supports the early application of noninvasive electrical stimulation (e.g. TENS) for improving clinical outcomes (i.e. reducing pain, improving ROM, and accelerating functional recovery after hip fractures). We could not find conclusive evidence on the effectiveness of using electrical stimulation to improve muscle strength. This review establishes the need for future additional high-quality trials in this field.

Hemodynamic responses to neuromuscular electrical stimulation and to metaboreflex evaluation

BACKGROUND

Metabolites produced during muscle exercise can sensitize types III and IV fibers, which account for increasing blood pressure (BP) and vascular resistance in non-exercising limbs, as well as for redistributing the blood flow to active muscles; reflex response is called metaboreflex. Neuromuscular electrical stimulation (NMES) induces greater local muscle metabolic demand than voluntary isometric contractions. Metabolic accumulation is essential to activate muscle metaboreflex; thus, the hypothesis of the current study is that one NMES session can induce metaboreflex with different hemodynamic responses in upper and lower limbs. Objective: investigating whether one acute NMES session could activate metaboreflex by inducing different hemodynamic responses between arms and legs.

METHODS

Twenty (20) healthy subjects (mean age = 47.7 ± 9.4 years, 13 women, mean body mass index = 26±3.4kg/m2) participated in this randomized crossover study. All participants were subjected to two NMES interventions, one in the upper limbs (UPL) and the other in the lower limbs (LL). Mean blood pressure (MBP), blood flow (BF) and vascular resistance (VR) at baseline were used to selectively evaluate metaboreflex responses during NMES interventions and recovery periods with, and without, postexercise circulatory occlusion (PECO+ and PECO-, respectively) through the area under the curve (AUC) in VR.

RESULTS

MBP increased by 13% during UPL interventions and only remained high during PECO+. Changes in MBP were not observed in LL, although BF in the contralateral leg has decreased by 14% during PECO+ protocol. Muscle metaboreflex activation (AUC differences in VR between PECO+ and PECO-) was not different between UPL and LL (p=0.655).

CONCLUSIONS

Acute NMES session has induced similar metaboreflex activation in both arms and legs, although hemodynamic responses differed between interventions.

Effects of Neuromuscular Electrical Stimulation Combined with Exercises versus an Exercise Program on the Physical Characteristics and Functions of the Elderly: A Randomized Controlled Trial

(1) Background-The application of neuromuscular electrical stimulation (NMES) combined with low-intensity exercise to the elderly can be more efficient than low-intensity exercise only in terms of delaying the loss of muscle mass. We aimed to assess the adjunct of NMES to low-intensity lower limb strengthening exercise to prevent falls in frail elderly for a relatively short period of 4 weeks. (2) Methods-Thirty elderly women aged 65 or above were randomly categorized into three groups: control group (CON, n = 8), exercise group (EX, n = 10), and NMES with exercise group (EX + NMES, n = 9). The exercise group took part in a lower limb strengthening exercise program for one hour three times a week for four weeks. Furthermore, the NMES with exercise group had added NMES stimulation when exercising. The limbs' muscle mass, body fat mass, calf circumference, grip force, five times sit-to-stand test, timed up-and-go test (TUG), one-leg stand test, and Y-balance test (YBT) were evaluated at baseline and 4 weeks after. (3) Results-Comparisons between the three groups showed that the TUG was significantly decreased and the YB was significantly increased in NMES with exercise group (p < 0.05). (4) Conclusions-These results suggested that a combination of NMES stimulation and exercises was more helpful in strengthening balance than exercises alone in the short term.

Rehabilitation to enable recovery from COVID-19: a rapid systematic review

Objectives

To establish the evidence for rehabilitation interventions tested in populations of patients admitted to ICU and critical care with severe respiratory illness, and consider whether the evidence is generalizable to patients with COVID-19.

Methods

The authors undertook a rapid systematic review. Medline (via OvidSP), CINAHL Complete (via EBSCOhost), Cochrane Library, Cochrane Database of Systematic Reviews and CENTRAL (via Wiley), Epistemonikos (via Epistemonikos.org), PEDro (via pedro.org.au) and OTseeker (via otseeker.com) searched to 7 May 2020. The authors included systematic reviews, RCTs and qualitative studies involving adults with respiratory illness requiring intensive care who received rehabilitation to enhance or restore resulting physical impairments or function. Data were extracted by one author and checked by a second. TIDier was used to guide intervention descriptions. Study quality was assessed using Critical Skills Appraisal Programme (CASP) tools.

Results

Six thousand nine hundred and three titles and abstracts were screened; 24 systematic reviews, 11 RCTs and eight qualitative studies were included. Progressive exercise programmes, early mobilisation and multicomponent interventions delivered in ICU can improve functional independence. Nutritional supplementation in addition to rehabilitation in post-ICU hospital settings may improve performance of activities of daily living. The evidence for rehabilitation after discharge from hospital following an ICU admission is inconclusive. Those receiving rehabilitation valued it, engendering hope and confidence.

Conclusions

Exercise, early mobilisation and multicomponent programmes may improve recovery following ICU admission for severe respiratory illness that could be generalizable to those with COVID-19. Rehabilitation interventions can bring hope and confidence to individuals but there is a need for an individualised approach and the use of behaviour change strategies. Further research is needed in post-ICU settings and with those who have COVID-19.



Registration: Open Science Framework https://osf.io/prc2y

Effects of neuromuscular electrical stimulation therapy on physical function in patients with COVID-19 associated pneumonia: Study protocol of a randomized controlled trial

Purpose

Neuromuscular electrical stimulation (NMES) has been considered as a promising approach for the early rehabilitation of patients during and/or after intensive care unit (ICU) stay. The overall objective of this study is to evaluate the NMES effectiveness to counteract the post-ICU impairment in physical function of COVID-19 patients. The specific aim of this manuscript is to describe the study design, protocol, content of interventions, primary and secondary outcomes and to discuss the clinical rehabilitation impact of the expected experimental results.

Methods

This prospective, randomized, controlled, parallel-group, single-blind trial will include 80 patients who had undergone mechanical or non-invasive ventilation following pneumonia-induced respiratory failure. Patients are randomized to a control group (routine physical therapy for 3 weeks) or a NMES group (routine physical therapy plus NMES of quadriceps and gastrocnemius muscles for 3 weeks). The primary outcome is physical performance assessed through the Short Physical Performance Battery (SPPB). Secondary outcomes include independence level, perceived fatigue, muscle strength, rectus femoris thickness, and walking performance. The SPBB and walking performance are assessed once (after the intervention), while all other outcomes are assessed twice (before and after the intervention).

Conclusion

NMES is a simple and non-invasive technique for muscle strengthening that is usually well tolerated, does not produce adverse effects, requires no or little cooperation from patients and is quite inexpensive. Therefore, proving the effectiveness of NMES therapy for physical and muscle function in COVID-19 patients could support its systematic incorporation in post-ICU rehabilitation protocols of patients presenting with post-intensive care syndrome.

Physical rehabilitation in Intensive Care Unit in acute respiratory distress syndrome patients with COVID-19

BACKGROUND

The risk of muscle weakness is high in the survivors of acute respiratory distress syndrome with COVID-19 following discharge from intensive care unit.

AIM

To evaluate the effects of early rehabilitation program in intensive care unit in patients with acute respiratory distress syndrome secondary to COVID-19.

DESIGN

The design of the study is observational.

SETTING

The setting of the study is inpatient.

POPULATION

Thirty-five patients with acute respiratory distress syndrome secondary to COVID-19 were enrolled.

METHODS

This study was performed in an intensive care unit of a university hospital. Early rehabilitation program consisting of passive or active range of motion exercises and neuromuscular electrical stimulation in addition to standard intensive care (N.=18) compared to standard intensive care (N.=17). Primary outcome was hand grip strength following discharge.

RESULTS

Rehab group had higher prevalence of chronic pulmonary diseases and neurologic diseases. There was no difference in hand grip or manual muscle strength following discharge between rehab and non-rehab groups. No adverse event was noted.

CONCLUSIONS

The results did not support the beneficial effects of early rehabilitation in intensive care unit on improving muscle strength. More patients with pulmonary and neurologic diseases in rehab group might impede the impact of rehabilitation on outcomes. On the other hand, these comorbidities underline the role and need of rehabilitation. It is safe both for the patients and the health care workers when necessary precautions are taken.

CLINICAL REHABILITATION IMPACT

This study guide how to rehabilitate patients with acute respiratory distress syndrome with COVID-19 during intensive care unit in a safe way.

Current Physical Therapy Practice in the Intensive Care Unit in Saudi Arabia: A Multicentre Cross-Sectional Survey

BACKGROUND

Early mobilisation of patients in the intensive care unit (ICU) is associated with positive health benefits. Research literature lacks insight into the current status of ICU physical therapy (PT) practice in the Kingdom of Saudi Arabia.

AIM

To determine the current standard of ICU PT practice, attitude, and barriers.

METHODS

A questionnaire was e-mailed to physiotherapists (PTs) working in the hospital. The questions pertained to experience, qualification, barriers, and most frequently encountered case scenarios in the ICU.

RESULTS

The response rate was 28.1% (124/442). Frequent cases referred to the PTs were traumatic paraplegia (n = 111, 89%) and stroke (n = 102, 82.3%) as compared to congestive heart failure (n = 20, 16.1%) and pulmonary infections (n = 7, 5.6%). The preferred treatment of choice among PTs was chest physiotherapy (n = 102, 82.2%) and positioning (n = 73, 58.8%), whereas functional electrical stimulation (n = 12, 9.6%) was least preferred irrespective of the condition. Perceived barriers in the ICU PT management were of low confidence in managing cases (n = 89, 71.7%) followed by inadequate training (n = 53, 42.7%), and the least quoted barrier was a communication gap between the critical care team members (n = 8, 6.4%).

CONCLUSION

PTs reported significant variation in the choice of treatment for different clinical cases inside ICU. The main barriers in the ICU setting were low confidence and inadequate training.

Quadriceps strength in intensive care unit survivors: Variability and influence of preadmission physical activity

BACKGROUND

Muscle weakness is common in patients who survive a stay in the intensive care unit (ICU). Quadriceps strength (QS) measurement allows evaluation of lower limb performances that are associated with mobility outcomes.

OBJECTIVES

The objective of the study was to characterise the range of QS in ICU survivors (ICUS) during their short-term evolution, by comparing them with surgical patients without critical illness and with healthy participants. The secondary aim was to explore whether physical activity before ICU admission influenced QS during that trajectory.

METHODS

Patients with length of ICU stay ≥2 days, adults scheduled for elective colorectal surgery, and young healthy volunteers were included. Maximal isometric QS was assessed using a handheld dynamometer and a previously validated standardised protocol. The dominant leg was tested in the supine position. ICUSs were tested in the ICU and 1 month after ICU discharge, while surgical patients were tested before and on the day after surgery, as well as 1 month after discharge. Healthy patients were tested once only. Patients were classified as physically inactive or active before admission from the self-report.

RESULTS

Thirty-eight, 32, and 34 participants were included in the ICU, surgical, and healthy groups, respectively. Demographic data were similar in the ICUS and surgical groups. In the ICU, QS was lower in the ICU group than in the surgical and healthy groups (3.01 [1.88-3.48], 3.38 [2.84-4.37], and 5.5 [4.75-6.05] N/kg, respectively). QS did not significantly improve 1 month after ICU discharge, excepted in survivors who were previously physically active (22/38, 56%): the difference between the two time points was -6.6 [-27.1 to -1.7]% vs 20.4 [-3.4 to 43.3]%, respectively, in physically inactive and active patients (p = 0.002).

CONCLUSIONS

Patients who survived an ICU stay were weaker than surgical patients. However, a huge QS heterogeneity was observed among them. Their QS did not improve during the month after ICU discharge. Physically inactive patients should be early identified as at risk of poorer recovery.

Self-directed home-based neuromuscular electrical stimulation (NMES) in patients with advanced cancer and poor performance status: a feasibility study

PURPOSE

Concurrent neuromuscular electrical stimulation (NMES) involving sub-tetanic low frequency and tetanic high frequency which targets aerobic and muscular fitness is a potential alternative to conventional exercise in cancer rehabilitation. However, its safety and feasibility in patients with advanced cancer are unknown. The aim of this feasibility study was to determine safety and feasibility and evaluate changes in functional and health-related quality of life (HR-QoL) outcomes in individuals with advanced cancer and poor performance status after concurrent NMES. These results should help inform the design of future studies.

METHODS

Participants with advanced cancer and poor performance status (Eastern Cooperative Oncology Group scale ≥ 2) (n = 18) were recruited. The intervention included a novel NMES intervention implemented over a 4-week period. Functional exercise capacity, lower limb muscle endurance and HR-QoL were measured by 6-min walk test (6MWT), 30-s sit-to-stand (30STS) and European Organization for Research and Treatment quality of life questionnaire core-30 (EORTC QLQ C30) pre and post-intervention. Participants unable to complete the 6-min walk test completed the timed up and go test. Participant experience and the impact of the intervention on daily life were investigated through semi-structured interviews.

RESULTS

Ten of 18 participants completed the intervention. No adverse events were reported. Seven of 8 participants improved 6MWT performance (2 of 2 improved timed up and go), 8 of 10 participants improved 30STS and 8 of 10 participants improved Global quality of life. Perceived benefits included improved mobility and muscle strength.

CONCLUSIONS

Neuromuscular electrical stimulation appears safe and feasible in advanced cancer and may improve physical and HR-QoL outcomes. Future prospective trials are warranted to confirm these findings prior to clinical implementation in an advanced cancer setting.

Breath-synchronized electrical stimulation of the expiratory muscles in mechanically ventilated patients: a randomized controlled feasibility study and pooled analysis

BACKGROUND

Expiratory muscle weakness leads to difficult ventilator weaning. Maintaining their activity with functional electrical stimulation (FES) may improve outcome. We studied feasibility of breath-synchronized expiratory population muscle FES in a mixed ICU population ("Holland study") and pooled data with our previous work ("Australian study") to estimate potential clinical effects in a larger group.

METHODS

Holland: Patients with a contractile response to FES received active or sham expiratory muscle FES (30 min, twice daily, 5 days/week until weaned). Main endpoints were feasibility (e.g., patient recruitment, treatment compliance, stimulation intensity) and safety. Pooled: Data on respiratory muscle thickness and ventilation duration from the Holland and Australian studies were combined (N = 40) in order to estimate potential effect size. Plasma cytokines (day 0, 3) were analyzed to study the effects of FES on systemic inflammation.

RESULTS

Holland: A total of 272 sessions were performed (active/sham: 169/103) in 20 patients (N = active/sham: 10/10) with a total treatment compliance rate of 91.1%. No FES-related serious adverse events were reported. Pooled: On day 3, there was a between-group difference (N = active/sham: 7/12) in total abdominal expiratory muscle thickness favoring the active group [treatment difference (95% confidence interval); 2.25 (0.34, 4.16) mm, P = 0.02] but not on day 5. Plasma cytokine levels indicated that early FES did not induce systemic inflammation. Using a survival analysis approach for the total study population, median ventilation duration and ICU length of stay were 10 versus 52 (P = 0.07), and 12 versus 54 (P = 0.03) days for the active versus sham group. Median ventilation duration of patients that were successfully extubated was 8.5 [5.6-12.2] versus 10.5 [5.3-25.6] days (P = 0.60) for the active (N = 16) versus sham (N = 10) group, and median ICU length of stay was 10.5 [8.0-14.5] versus 14.0 [9.0-19.5] days (P = 0.36) for those active (N = 16) versus sham (N = 8) patients that were extubated and discharged alive from the ICU. During ICU stay, 3/20 patients died in the active group versus 8/20 in the sham group (P = 0.16).

CONCLUSION

Expiratory muscle FES is feasible in selected ICU patients and might be a promising technique within a respiratory muscle-protective ventilation strategy. The next step is to study the effects on weaning and ventilator liberation outcome.

TRIAL REGISTRATION

ClinicalTrials.gov, ID NCT03453944. Registered 05 March 2018-Retrospectively registered, https://clinicaltrials.gov/ct2/show/NCT03453944 .

Muscle Hypertrophy and Architectural Changes in Response to Eight-Week Neuromuscular Electrical Stimulation Training in Healthy Older People

Loss of muscle mass of the lower limbs and of the spine extensors markedly impairs locomotor ability and spine stability in old age. In this study, we investigated whether 8 w of neuromuscular electrical stimulation (NMES) improves size and architecture of the lumbar multifidus (LM) and vastus lateralis (VL) along with locomotor ability in healthy older individuals. Eight volunteers (aged 65 ≥ years) performed NMES 3 times/week. Eight sex- and age-matched individuals served as controls. Functional tests (Timed Up and Go test (TUG) and Five Times Sit-to-Stand Test (FTSST)), VL muscle architecture (muscle thickness (MT), pennation angle (PA), and fiber length (FL)), along with VL cross-sectional area (CSA) and both sides of LM were measured before and after by ultrasound. By the end of the training period, MT and CSA of VL increased by 8.6% and 11.4%, respectively. No significant increases were observed in FL and PA. LM CSA increased by 5.6% (left) and 7.1% (right). Interestingly, all VL architectural parameters significantly decreased in the control group. The combined NMES had a large significant effect on TUG (r = 0.50, p = 0.046). These results extend previous findings on the hypertrophic effects of NMES training, suggesting to be a useful mean for combating age-related sarcopenia.

Bioactive polymeric materials and electrical stimulation strategies for musculoskeletal tissue repair and regeneration

Electrical stimulation (ES) is predominantly used as a physical therapy modality to promote tissue healing and functional recovery. Research efforts in both laboratory and clinical settings have shown the beneficial effects of this technique for the repair and regeneration of damaged tissues, which include muscle, bone, skin, nerve, tendons, and ligaments. The collective findings of these studies suggest ES enhances cell proliferation, extracellular matrix (ECM) production, secretion of several cytokines, and vasculature development leading to better tissue regeneration in multiple tissues. However, there is still a gap in the clinical relevance for ES to better repair tissue interfaces, as ES applied clinically is ineffective on deeper tissue. The use of a conducting material can transmit the stimulation applied from skin electrodes to the desired tissue and lead to an increased function on the repair of that tissue. Ionically conductive (IC) polymeric scaffolds in conjunction with ES may provide solutions to utilize this approach effectively. Injectable IC formulations and their scaffolds may provide solutions for applying ES into difficult to reach tissue types to enable tissue repair and regeneration. A better understanding of ES-mediated cell differentiation and associated molecular mechanisms including the immune response will allow standardization of procedures applicable for the next generation of regenerative medicine. ES, along with the use of IC scaffolds is more than sufficient for use as a treatment option for single tissue healing and may fulfill a role in interfacing multiple tissue types during the repair process.

Estimating the sample mean and standard deviation from commonly reported quantiles in meta-analysis

Researchers increasingly use meta-analysis to synthesize the results of several studies in order to estimate a common effect. When the outcome variable is continuous, standard meta-analytic approaches assume that the primary studies report the sample mean and standard deviation of the outcome. However, when the outcome is skewed, authors sometimes summarize the data by reporting the sample median and one or both of (i) the minimum and maximum values and (ii) the first and third quartiles, but do not report the mean or standard deviation. To include these studies in meta-analysis, several methods have been developed to estimate the sample mean and standard deviation from the reported summary data. A major limitation of these widely used methods is that they assume that the outcome distribution is normal, which is unlikely to be tenable for studies reporting medians. We propose two novel approaches to estimate the sample mean and standard deviation when data are suspected to be non-normal. Our simulation results and empirical assessments show that the proposed methods often perform better than the existing methods when applied to non-normal data.

Functional, physiological and subjective responses to concurrent neuromuscular electrical stimulation (NMES) exercise in adult cancer survivors: a controlled prospective study

The primary aim of this study was to investigate the functional, physiological and subjective responses to NMES exercise in cancer patients. Participants with a cancer diagnosis, currently undergoing treatment, and an had an Eastern Cooperative Oncology Group (ECOG) performance status (ECOG) of 1 and 2 were recommended to participate by their oncologist. Following a 2-week, no-NMES control period, each participant was asked to undertake a concurrent NMES exercise intervention over a 4-week period. Functional muscle strength [30 s sit-to-stand (30STS)], mobility [timed up and go (TUG)], exercise capacity [6-min walk test (6MWT)] and health related quality of life (HR-QoL) were assessed at baseline 1 (BL1), 2-week post control (BL2) and post 4-week NMES exercise intervention (POST). Physiological and subjective responses to LF-NMES were assessed during a 10-stage incremental session, recorded at BL2 and POST. Fourteen participants [mean age: 62 years (10)] completed the intervention. No adverse events were reported. 30STS (+ 2.4 reps, p = .007), and 6MWT (+ 44.3 m, p = .028) significantly improved after the intervention. No changes in TUG or HR-QoL were observed at POST. Concurrent NMES exercise may be an effective exercise intervention for augmenting physical function in participants with cancer and moderate and poor functional status. Implications for cancer survivors: By allowing participants to achieve therapeutic levels of exercise, concurrent NMES may be an effective supportive intervention in cancer rehabilitation.

Brain-Machine Neurofeedback: Robotics or Electrical Stimulation?

Neurotechnology such as brain-machine interfaces (BMI) are currently being investigated as training devices for neurorehabilitation, when active movements are no longer possible. When the hand is paralyzed following a stroke for example, a robotic orthosis, functional electrical stimulation (FES) or their combination may provide movement assistance; i.e., the corresponding sensory and proprioceptive neurofeedback is given contingent to the movement intention or imagination, thereby closing the sensorimotor loop. Controlling these devices may be challenging or even frustrating. Direct comparisons between these two feedback modalities (robotics vs. FES) with regard to the workload they pose for the user are, however, missing. Twenty healthy subjects controlled a BMI by kinesthetic motor imagery of finger extension. Motor imagery-related sensorimotor desynchronization in the EEG beta frequency-band (17–21 Hz) was turned into passive opening of the contralateral hand by a robotic orthosis or FES in a randomized, cross-over block design. Mental demand, physical demand, temporal demand, performance, effort, and frustration level were captured with the NASA Task Load Index (NASA-TLX) questionnaire by comparing these workload components to each other (weights), evaluating them individually (ratings), and estimating the respective combinations (adjusted workload ratings). The findings were compared to the task-related aspects of active hand movement with EMG feedback. Furthermore, both feedback modalities were compared with regard to their BMI performance. Robotic and FES feedback had similar workloads when weighting and rating the different components. For both robotics and FES, mental demand was the most relevant component, and higher than during active movement with EMG feedback. The FES task led to significantly more physical (p = 0.0368) and less temporal demand (p = 0.0403) than the robotic task in the adjusted workload ratings. Notably, the FES task showed a physical demand 2.67 times closer to the EMG task, but a mental demand 6.79 times closer to the robotic task. On average, significantly more onsets were reached during the robotic as compared to the FES task (17.22 onsets, SD = 3.02 vs. 16.46, SD = 2.94 out of 20 opportunities; p = 0.016), even though there were no significant differences between the BMI classification accuracies of the conditions (p = 0.806; CI = −0.027 to −0.034). These findings may inform the design of neurorehabilitation interfaces toward human-centered hardware for a more natural bidirectional interaction and acceptance by the user.

Feasibility of eccentric overloading and neuromuscular electrical stimulation to improve muscle strength and muscle mass after treatment for head and neck cancer

PURPOSE

Treatment of head and neck cancer (HNC) results in severe weight loss, mainly due to the loss of lean body mass. Consequently, decreases in muscular strength and health-related quality of life (HRQL) occur. This study investigated the feasibility of a 12-week novel strength training (NST) and conventional strength training (CST) intervention delivered after HNC treatment.

METHODS

Participants were randomized to a NST group (n = 11) involving eccentric overloaded strength training and neuromuscular electrical stimulation (NMES), or a CST group (n = 11) involving dynamic resistance exercises matched for training volume. Feasibility outcomes included recruitment, completion, adherence, and evidence of progression. A neuromuscular assessment involving maximal isometric voluntary contractions (MIVCs) in the knee extensors was evaluated prior to and during incremental cycling to volitional exhaustion at baseline and after the interventions. Anthropometrics and patient-reported outcomes (PROs) were also assessed.

RESULTS

Although recruitment was challenging, completion was 100% in NST and 82% in CST. Adherence was 92% in NST and 81% in CST. Overall, MIVC increased by 19 ± 23%, muscle cross-sectional area improved 18 ± 22%, cycling exercise time improved by 18 ± 13%, and improvements in HRQL and fatigue were clinically relevant.

CONCLUSIONS

Both interventions were found to be feasible for HNC patients after treatment. Strength training significantly improved maximal muscle strength, muscle cross-sectional area, and PROs after HNC treatment. Future research should include fully powered trials and consider the use of eccentric overloading and NMES during HNC treatment.

IMPLICATIONS FOR CANCER SURVIVORS

Eccentric- and NMES-emphasized strength training may be useful alternatives to conventional strength training after HNC treatment.

Intervention effect of neuromuscular electrical stimulation on ICU acquired weakness: A meta-analysis

Objective

The early use of neuromuscular electrical stimulation (NMES) to prevent intensive care unit-acquired weakness (ICU-AW) in critical patients is still a controversial topic. We conducted a systematic review to clarify the effectiveness of NMES in preventing ICU-AW.

Methods

The Cochrane Library, PubMed, EMBASE, MEDLINE, Web of Science, Ovid, CNKI, Wanfang, VIP, China Biology Medicine disc (CBMdisc) and other databases were searched for randomized controlled trials on the influence of NMES on ICU-AW. The studies were selected according to the inclusion and exclusion criteria. After data and quality were evaluated, a meta-analysis was performed by RevMan 5.3 software.

Results

A total of 11 randomized controlled trials with 576 patients were included. The meta-analysis results showed that NMES can improve muscle strength [MD = 1.78, 95% CI (0.44, 3.12, P = 0.009); shorten the mechanical ventilation (MV) time [SMD = −0.65, 95% CI (−1.03, −0.27, P = 0.001], ICU length of stay [MD = −3.41, 95% CI (−4.58, −4.24), P < 0.001], and total length of stay [MD = −3.97, 95% CI (−6.89, −1.06, P = 0.008]; improve the ability of patients to perform activities of daily living [SMD = 0.9, 95% CI (0.45, 1.35), P = 0.001]; and increase walking distance [MD = 239.03, 95% CI (179.22298.85), P < 0.001]. However, there is no evidence indicating that NMES can improve the functional status of ICU patients during hospitalization, promote the early awakening of patients or reduce mortality (P > 0.05).

Conclusion

Early implementation of the NMES intervention in ICU patients can prevent ICU-AW and improve their quality of life by enhancing their muscle strength and shortening the MV duration, length of stay in the ICU and total length of stay in the hospital.

Neuromuscular electrical stimulation in critically ill traumatic brain injury patients attenuates muscle atrophy, neurophysiological disorders, and weakness: a randomized controlled trial

Background

Critically ill traumatic brain injury (TBI) patients experience extensive muscle damage during their stay in the intensive care unit. Neuromuscular electrical stimulation (NMES) has been considered a promising treatment to reduce the functional and clinical impacts of this. However, the time needed for NMES to produce effects over the muscles is still unclear. This study primarily aimed to assess the time needed and effects of an NMES protocol on muscle architecture, neuromuscular electrophysiological disorder (NED), and muscle strength, and secondarily, to evaluate the effects on plasma systemic inflammation, catabolic responses, and clinical outcomes.

Methods

We performed a randomized clinical trial in critically ill TBI patients. The control group received only conventional physiotherapy, while the NMES group additionally underwent daily NMES for 14 days in the lower limb muscles. Participants were assessed at baseline and on days 3, 7, and 14 of their stay in the intensive care unit. The primary outcomes were assessed with muscle ultrasound, neuromuscular electrophysiology, and evoked peak force, and the secondary outcomes with plasma cytokines, matrix metalloproteinases, and clinical outcomes.

Results

Sixty participants were randomized, and twenty completed the trial from each group. After 14 days, the control group presented a significant reduction in muscle thickness of tibialis anterior and rectus femoris, mean of - 0.33 mm (- 14%) and - 0.49 mm (- 21%), p < 0.0001, respectively, while muscle thickness was preserved in the NMES group. The control group presented a higher incidence of NED: 47% vs. 0% in the NMES group, p < 0.0001, risk ratio of 16, and the NMES group demonstrated an increase in the evoked peak force (2.34 kg/f, p < 0.0001), in contrast to the control group (- 1.55 kg/f, p < 0.0001). The time needed for the NMES protocol to prevent muscle architecture disorders and treat weakness was at least 7 days, and 14 days to treat NED. The secondary outcomes exhibited less precise results, with confidence intervals that spanned worthwhile or trivial effects.

Conclusions

NMES applied daily for fourteen consecutive days reduced muscle atrophy, the incidence of NED, and muscle weakness in critically ill TBI patients. At least 7 days of NMES were required to elicit the first significant results.

Trial registration

The trial was registered at ensaiosclinicos.gov.br under protocol RBR-8kdrbz on 17 January 2016.

Neuromuscular electrical stimulation-promoted plasticity of the human brain

The application of neuromuscular electrical stimulation (NMES) to paretic limbs has demonstrated utility for motor rehabilitation following brain injury. When NMES is delivered to a mixed peripheral nerve, typically both efferent and afferent fibres are recruited. Muscle contractions brought about by the excitation of motor neurons are often used to compensate for disability by assisting actions such as the formation of hand aperture, or by preventing others including foot drop. In this context, exogenous stimulation provides a direct substitute for endogenous neural drive. The goal of the present narrative review is to describe the means through which NMES may also promote sustained adaptations within central motor pathways, leading ultimately to increases in (intrinsic) functional capacity. There is an obvious practical motivation, in that detailed knowledge concerning the mechanisms of adaptation has the potential to inform neurorehabilitation practice. In addition, responses to NMES provide a means of studying CNS plasticity at a systems level in humans. We summarize the fundamental aspects of NMES, focusing on the forms that are employed most commonly in clinical and experimental practice. Specific attention is devoted to adjuvant techniques that further promote adaptive responses to NMES thereby offering the prospect of increased therapeutic potential. The emergent theme is that an association with centrally initiated neural activity, whether this is generated in the context of NMES triggered by efferent drive or via indirect methods such as mental imagery, may in some circumstances promote the physiological changes that can be induced through peripheral electrical stimulation.

Efeitos do exercício passivo precoce em cicloergômetro na espessura muscular do quadríceps femoral de pacientes críticos: estudo-piloto randomizado controlado

RESUMO O objetivo deste estudo foi avaliar os efeitos do exercício passivo precoce em cicloergômetro na espessura muscular (EM) do quadríceps femoral (EMQ) de pacientes críticos admitidos em uma Unidade de Terapia Intensiva (UTI) de um hospital universitário terciário. O método utilizado foi um estudo-piloto randomizado controlado conduzido em uma amostra de 24 pacientes (51±18,11 anos, 16 do sexo masculino), com 24 a 48 horas de ventilação mecânica (VM), aleatoriamente divididos em dois grupos: grupo-controle (n=12), que recebeu a fisioterapia convencional; e grupo-intervenção (n=12), que recebeu o exercício passivo em cicloergômetro, uma vez ao dia, durante o período de sete dias do protocolo, em adição à fisioterapia convencional. A EMQ foi mensurada através da ultrassonografia. A primeira medida ultrassonográfica foi realizada entre as primeiras 48 horas de VM e a segunda ao término do protocolo. Não houve diferenças significativas na EMQ esquerda (27,29±5,86mm vs. 25,95±10,89mm; p=0,558) e direita (24,96±5,59mm vs 25,9±9,21mm; p=0,682) do grupo-controle e na EMQ esquerda (27,2±7,38mm vs 29,57±7,89mm; p=0,299) e direita (26,67±8,16mm vs 28,65±8,04mm; p=0,381) do grupo-intervenção. Na comparação entre os grupos, não houve alterações significativas em relação à EMQ esquerda (3,61±1,07mm; p=0,248) e a EMQ direita (2,75±0,85mm; p=0,738). Os resultados deste estudo-piloto demonstraram que a aplicação precoce do exercício passivo em cicloergômetro não promoveu mudanças significativas na espessura da camada muscular avaliada. No entanto, nossos achados sinalizam que a fisioterapia convencional foi capaz de preservar a EMQ de pacientes críticos admitidos em UTI.

Dose-Response Relationship Between Neuromuscular Electrical Stimulation and Muscle Function in People With Rheumatoid Arthritis

BACKGROUND

Neuromuscular electrical stimulation (NMES) is a viable intervention for improving impaired muscle function in individuals with rheumatoid arthritis (RA). However, there is limited evidence about the dose-response relationship between NMES and muscle function in these individuals.

OBJECTIVE

The objectives of this study were to investigate the dose-response relationship between NMES and muscle function in individuals with RA and to establish the minimal NMES training intensity for promoting improvements.

DESIGN

This study was a secondary analysis of data obtained before and after an NMES intervention in a randomized study.

METHODS

The study took place at a research clinic. Only adults diagnosed with RA were included. The intervention consisted of 36 NMES treatment sessions for the quadriceps muscles over 16 weeks. Muscle function was measured before and after the intervention; quadriceps cross-sectional area and muscle quality were assessed using computed tomography, and strength was measured with an isokinetic dynamometer. NMES training intensity was calculated as a percentage by dividing NMES-elicited quadriceps muscle torque by the maximum voluntary isometric contraction. Improvements in muscle function were calculated using paired-sample t tests. The dose-response relationship was determined using curve estimation regression statistics. The minimum NMES training intensity was defined as that sufficient to significantly improve all muscle function measures.

RESULTS

Twenty-four people (48 legs) participated (75% women; mean [SD] age = 58 [8] years; mean body mass index = 32 [7] kg/m2). Quadriceps cross-sectional area, muscle quality, and strength improved after the intervention. Associations between NMES training intensity and muscle quality (r2 = 0.20) and strength (r2 = 0.23) were statistically significant, but that between NMES training intensity and muscle cross-sectional area was not (r2 = 0.02). The minimum NMES training intensity necessary to improve all measures of muscle function ranged from 11% to 20% of the maximum voluntary isometric contraction.

LIMITATIONS

The relatively small sample size was a limitation.

CONCLUSIONS

The minimum NMES training intensity for significant gains in muscle function was ∼15%. Higher NMES intensities may promote better muscle quality and strength in individuals with RA.

Repetitive vascular occlusion stimulus (RVOS) versus standard care to prevent muscle wasting in critically ill patients (ROSProx):a study protocol for a pilot randomised controlled trial

BACKGROUND

Forty per cent of critically ill patients are affected by intensive care unit-acquired weakness (ICU-AW), to which skeletal muscle wasting makes a substantial contribution. This can impair outcomes in hospital, and can cause long-term physical disability after hospital discharge. No effective mitigating strategies have yet been identified. Application of a repetitive vascular occlusion stimulus (RVOS) a limb pressure cuff inducing brief repeated cycles of ischaemia and reperfusion, can limit disuse muscle atrophy in both healthy controls and bed-bound patients recovering from knee surgery. We wish to determine whether RVOS might be effective in mitigating against muscle wasting in the ICU. Given that RVOS can also improve vascular function in healthy controls, we also wish to assess such effects in the critically ill. We here describe a pilot study to assess whether RVOS application is safe, tolerable, feasible and acceptable for ICU patients.

METHODS

This is a randomised interventional feasibility trial. Thirty-two ventilated adult ICU patients with multiorgan failure will be recruited within 48 h of admission and randomised to either the intervention arm or the control arm. Intervention participants will receive RVOS twice daily (except only once on day 1) for up to 10 days or until ICU discharge. Serious adverse events and tolerability (pain score) will be recorded; feasibility of trial procedures will be assessed against pre-specified criteria and acceptability by semi-structured interview. Together with vascular function, muscle mass and quality will be assessed using ultrasound and measures of physical function at baseline, on days 6 and 11 of study enrolment, and at ICU and hospital discharge. Blood and urine biomarkers of muscle metabolism, vascular function, inflammation and DNA damage/repair mechanism will also be analysed. The Health questionnaire will be completed 3 months after hospital discharge.

DISCUSSION

If this study demonstrates feasibility, the derived data will be used to inform the design (and sample size) of an appropriately-powered prospective trial to clarify whether RVOS can help preserve muscle mass/improve vascular function in critically ill patients.

TRIAL REGISTRATION

ISRCTN Registry, ISRCTN44340629. Registered on 26 October 2017.

The effect of early mobilization in critically ill patients: A meta-analysis

BACKGROUND

The aim of this meta-analysis was to assess if early mobilization and rehabilitation in the intensive care unit (ICU) could reduce ICU-acquired weakness (ICU-AW), improve functional recovery, improve muscle strength, shorten the length of ICU and hospital stays, and reduce the mortality rate.

METHODS

A comprehensive literature search in PubMed, Embase, Web of Science, SinoMed (Chinese BioMedical Literature Service System, China), and National Knowledge Infrastructure, China (CNKI) was performed. Results were expressed as a risk ratio (RR) with 95% confidence intervals (95% CIs) or weight mean difference (WMD) with 95% CIs. Pooled estimates were calculated using a fixed-effects or random-effects model according to the heterogeneity among studies.

RESULTS

Fifteen randomized controlled trials involving a total of 1941 patients were included in this meta-analysis. Pooled estimates suggested that early mobilization significantly reduced the incidence of ICU-AW (RR = 0.49, 95% CI: 0.26, 0.91; P = .025), shortened the length of ICU (WMD = -1.82 days, 95% CI: -2.88, -0.76; P = .001) and hospital (WMD = -3.90 days, 95% CI: -5.94, -1.85; P < .001) stays, and improved the Medical Research Council score (WMD = 4.47, 95% CI: 1.43, 7.52; P = .004) and Barthel Index score at hospital discharge (WMD = 21.44, 95% CI: 10.97, 31.91; P < .001). Moreover, early mobilization also decreased complications such as deep vein thrombosis (RR = 0.16, 95% CI: 0.04, 0.59; P = .006), ventilator-associated pneumonia (RR = 0.26, 95% CI: 0.11, 0.63; P = .003), and pressure sores (RR = 0.14, 95% CI: 0.04, 0.44; P = .001). However, early mobilization did not reduce the ICU mortality rate (RR = 1.31, 95% CI: 0.97, 1.76; P = .074), improve the handgrip strength (WMD = 4.03 kg, 95% CI: -0.68, 8.74; P = .094), and shorten the duration of mechanical ventilation (WMD = 0.20 days, 95% CI: -0.10, 0.50; P = .194).

CONCLUSION

This study indicated that early mobilization was effective in preventing the occurrence of ICU-AW, shortening the length of ICU and hospital stay, and improving the functional mobility. However, it had no effect on the ICU mortality rate and ventilator-free days.

RELEVANCE TO CLINICAL PRACTICE

ICU-AW is a common neuromuscular complication of critical illness, and it is predictive of adverse outcomes. Early mobilization of critically ill patients is a candidate intervention to reduce the incidence and severity of ICU-AW. Some clinical studies have demonstrated this, whereas others found opposite results. The aim of our study is to assess if early mobilization and rehabilitation in the ICU could reduce the ICU-AW, improve functional recovery, improve muscle strength, shorten length of ICU and hospital stay, and reduce the mortality rate.

Effects of neuromuscular electrical stimulation in critically ill patients: A systematic review and meta-analysis of randomised controlled trials

OBJECTIVES

We performed a systematic review and meta-analysis to examine the effect of neuromuscular electrical stimulation (NES) on prevention of critical care myopathy and its effect on various clinical outcomes in the intensive care unit (ICU).

REVIEW METHODS USED

This study involved systematic review and meta-analysis of randomised controlled trials (RCTs) comparing NES (applied to different muscle groups combined with usual care) and usual care (passive and active exercises along with early mobilisation and rehabilitation). Included studies enrolled adult patients managed in the ICU for medical or surgical diseases who were or were not mechanically ventilated. The primary outcome was global muscle strength measured by the Medical Research Council grading system. Secondary outcomes included ICU mortality, duration of mechanical ventilation (MV), and ICU length of stay. Risk ratio for dichotomous data and mean difference (MD) for continuous data with their corresponding 95% confidence interval (CI) were calculated.

DATA SOURCE

A search in major electronic databases, including PubMed, Cochrane Library, and Embase, from inception to November 2018 was carried out.

RESULTS

Six RCTs were included, representing 718 patients. The mean age 60 ± 15.3 years, and 60.6% were male. There was no significant difference between NES and usual care on global muscle strength measured by Medical Research Council grading system (MD: 0.45; 95% CI: -2.89 to 3.80; p = 0.79), ICU mortality (risk ratio: 1.30; 95% CI: 0.95-1.78; p = 0.10), duration of MV (days) (MD: -2.07; 95% CI: -5.06 to 0.92; p = 0.18), or ICU length of stay (days) (MD: -3.06; 95% CI: -9.79 to 3.68; p = 0.37) in comparison with the usual therapy alone in critically ill patients.

CONCLUSION

NES combined with usual care was not associated with significant differences in global muscle strength, ICU mortality, duration of MV, or ICU length of stay in comparison with usual care alone in critically ill patients. Further RCTs are needed to determine patients with maximum benefit and to examine NES safety and efficacy.

Safety of long-term electrical peripheral nerve stimulation: review of the state of the art

BACKGROUND

Electrical stimulation of peripheral nerves is used in a variety of applications such as restoring motor function in paralyzed limbs, and more recently, as means to provide intuitive sensory feedback in limb prostheses. However, literature on the safety requirements for stimulation is scarce, particularly for chronic applications. Some aspects of nerve interfacing such as the effect of stimulation parameters on electrochemical processes and charge limitations have been reviewed, but often only for applications in the central nervous system. This review focuses on the safety of electrical stimulation of peripheral nerve in humans.

METHODS

We analyzed early animal studies evaluating damage thresholds, as well as more recent investigations in humans. Safety requirements were divided into two main categories: passive and active safety. We made the distinction between short-term (< 30 days) and chronic (> 30 days) applications, as well as between electrode preservation (biostability) and body tissue healthy survival (harmlessness). In addition, transferability of experimental results between different tissues and species was considered.

RESULTS

At present, extraneural electrodes have shown superior long-term stability in comparison to intraneural electrodes. Safety limitations on pulse amplitude (and consequently, charge injection) are dependent on geometrical factors such as electrode placement, size, and proximity to the stimulated fiber. In contrast, other parameters such as stimulation frequency and percentage of effective stimulation time are more generally applicable. Currently, chronic stimulation at frequencies below 30 Hz and percentages of effective stimulation time below 50% is considered safe, but more precise data drawn from large databases are necessary. Unfortunately, stimulation protocols are not systematically documented in the literature, which limits the feasibility of meta-analysis and impedes the generalization of conclusions. We therefore propose a standardized list of parameters necessary to define electrical stimulation and allow future studies to contribute to meta-analyses.

CONCLUSION

The safety of chronic continuous peripheral nerve stimulation at frequencies higher than 30 Hz has yet to be documented. Precise parameter values leading to stimulation-induced depression of neuronal excitability (SIDNE) and neuronal damage, as well as the transition between the two, are still lacking. At present, neural damage mechanisms through electrical stimulation remain obscure.