Effect of adding neuromuscular electrical stimulation for patients with moderate to severe chronic obstructive pulmonary disease: Systematic review and meta-analysis

BACKGROUND

Healthcare providers have faced challenges for patients with moderate and severe chronic obstructive pulmonary disease (COPD) in conducting their pulmonary rehabilitation due to dyspnea and exercise intolerance. Neuromuscular electrical stimulation (NMES) has been used to improve the muscle group's power and endurance without adding pulmonary workload, which might be used as a potential adjuvant rehabilitation method and thus to improve patients' pulmonary functions.

METHODS

This was a systematic review and meta-analysis of randomized controlled trials. Data were retrieved from PubMed, CINAHL, Academic Search Complete, Cochrane Library, and Airiti Library databases from the inception of the database to December 2022. The Cochrane Collaboration tool was used to assess the risk of bias. Two reviewers independently assessed, extracted, and appraised the included studies. Then, the grading of recommendations, assessment, development, and evaluation (GRADE) methodology was used for assessing the certainty of evidence. The pooled estimates were calculated using a random-effects model.

RESULTS

In total, 19 studies involving 589 moderate to severe COPD patients were analyzed. Compared with controls, adding NMES to pulmonary rehabilitation could significantly increase exercise capacity, physical activity function, and health-related quality of life (HRQoL) (all p < 0.05). The GRADE results showed low to very low certainty of evidence levels.

CONCLUSION

NMES could improve exercise capacity and reduce the perceived sensation of dyspnea during exercise and is recommended as an effective adjuvant training modality in the rehabilitation for moderate to severe COPD patients.

20 years of neuromuscular electrical stimulation in COPD

Although a lung disease, COPD is also associated with extrapulmonary manifestations including, among others, limb muscle dysfunction. Limb muscle dysfunction is a key systemic consequence of COPD that impacts patients' physical activity, exercise tolerance, quality of life and survival. Deconditioning is the main mechanism underlying the development of limb muscle dysfunction in COPD, which can be partially improved with exercise. However, some patients may not be able to tolerate exercise because of incapacitating breathlessness or unwillingness to undertake whole-body exercise. Alternative training modalities that do not give rise to dyspnoea, such as neuromuscular electrical stimulation (NMES), are urged. Over the past 20 years, NMES in COPD has presented conflicting conclusions in meta-analysis. In this review, we try to understand the reason for this result by analysing possible biases and factors that brought conflicting conclusions. We discuss the population (the intervention group, but also the control group), the outcome measures, the frequency of stimulation, the rehabilitation protocol (i.e. NMES alone versus standard care/rehabilitation or NMES plus conventional exercise training versus conventional exercise training alone or NMES versus sham treatment) and the trial design. The main reason for this discrepancy is the lack of dedicated guidelines for NMES. Further research is urged to determine the optimal parameters for an NMES programme. Despite this, NMES appears to be an effective means of enhancing quadriceps strength and exercise capacity in COPD with the potential to break the vicious circle induced by the disease and COPD patients' lifestyle.

Effects of neuromuscular electrical stimulation on exercise capacity, muscle strength and quality of life in COPD patients: A Systematic Review with Meta-Analysis

OBJECTIVE

To determine the effects of neuromuscular electrical stimulation on disabilities and activity limitation of individuals affected by chronic obstructive pulmonary disease.

DATA SOURCES

MEDLINE, PEDro database, Cochrane Controlled Trials Register, and SciELO, were searched from inception until October 2021.

REVIEW METHODS

Inclusion criteria were patients with COPD, randomized controlled trials comparing neuromuscular electrical stimulation alone or combined conventional pulmonary rehabilitation and neuromuscular electrical stimulation versus control or sham or pulmonary rehabilitation in disabilities and activity limitation in COPD. There were no mandatory language or publication date restrictions. Two reviewers selected studies independently. Weighted mean differences and 95% confidence intervals were calculated.

RESULTS

32 studies met the study criteria, including 1.269 participants. Neuromuscular electrical stimulation improved exercise capacity (MD 1.10, 95% CI: 0.33, 1.86, N = 147), and muscle strength (0.53, 95% CI: 0.20, 0.87, N = 147) compared to sham group. Combined neuromuscular electrical stimulation and conventional rehabilitation improved exercise capacity (MD 34.28 meters, 95% CI: 6.84, 61.73, N = 262) compared to conventional rehabilitation alone. No adverse events were reported.

CONCLUSIONS

Neuromuscular electrical stimulation resulted in small improvement in disabilities and activity limitation (below the MCID) in COPD. Thus, the inclusion of neuromuscular electrical stimulation in rehabilitation programs must consider the cost Because of inadequate methodological conduction and reporting of methods, some studies were of low quality.

The narrative review of chronic obstructive pulmonary disease management in Turkey: medical treatment, pulmonary rehabilitation and endobronchial volume reduction

Chronic obstructive pulmonary disease (COPD) is one of the most common chronic diseases. In Turkey, the prevalence of COPD has been shown at rates of 9.1% to 19.1%, and COPD was found to be the third leading cause of mortality and eighth leading cause of disability. In several national multicentral studies, a high rate of non-adherence to pharmacologic treatment according to GOLD was found to be high, and the most commonly prescribed treatment was the triple regimen. The most important non-pharmacologic treatment of COPD is pulmonary rehabilitation (PR), which is also highly recommended in Turkey, but it is also underutilized, like in other countries. Awareness of healthcare professionals and patients should increase in Turkey. The recommendations in content and modality of programs are similar to international guidelines. Another non-pharmacologic treatment is endobronchial volume reduction (EBVR). Although there is limited number of studies about EBVR, in national reports, the importance of patient selection, method, close follow-up after intervention, and applications in experienced centers are emphasized to decrease the economic burden of this expensive treatment. There is still great need for further randomized studies about pharmacologic and non-pharmacologic treatment and additionally, a close collaboration between healthcare professionals, physicians, professional societies of pulmonology, planners of reimbursement system, patients, patient advocacy groups and the general public should be established.

Effects of neuromuscular electrical stimulation on exercise capacity and quality of life in COPD patients: a systematic review and meta-analysis

Neuromuscular electrical stimulation (NMES) has been shown to produce benefits in the muscle function of chronic obstructive pulmonary disease (COPD) patients. The definite effectiveness of NMES, applied in isolation or concurrently with conventional pulmonary rehabilitation (PR) or exercise training, remains unclear. This review was to determine the effects of NMES on exercise capacity, functional performance, symptoms, and health-related quality of life (HRQoL) in COPD patients. Electronic databases (PubMed, Embase, Web of Science, the Cochrane Library) were searched for relevant randomized controlled trials (RCTs). Two investigators independently screened the eligible studies up to February 2020 that used NMES as the intervention group. The outcome measures were 6-min walking distance (6MWD), peak rate of oxygen uptake (VO₂ peak), St George’s Respiratory Questionnaire (SGRQ), and symptoms of dyspnoea and fatigue. Data were extracted using a predefined table and papers were appraised using Downs and Black tool. We analyzed 13 RCTs with 447 COPD patients. In the analysis of 6MWD, pooled estimates showed a significant increase in the NMES group, compared with the control group (mean difference (MD) = 27.05, 95% confidence interval (CI): 8.46–45.63, P<0.001). There were also improvements in symptoms of dyspnea or leg fatigue, and reduction in London Chest Activity of Daily Living (LCADL) scores. No statistically significant difference was observed in VO₂ peak, peak power, and SGRQ. NMES could improve exercise capacity and reduce perceived sensation of dyspnea during exercise in patients with COPD, but not to be recommended as an effective alternative training modality in the rehabilitation of stable COPD patients.

Minimal Clinically Important Difference for Quadriceps Muscle Strength in People with COPD following Pulmonary Rehabilitation

Quadriceps strength training is a key component of pulmonary rehabilitation (PR). Clinical interpretability of changes in muscle strength following PR is however limited due to the lack of cut-off values to define clinical improvement. This study estimated the minimal clinically important difference (MCID) for the isotonic and isometric quadriceps muscle strength assessed with the one-repetition maximum (1RM) and hand-held dynamometry (HHD) in people with chronic obstructive pulmonary disease (COPD) following PR.A secondary analysis of a real life non-randomised controlled study was conducted in people with COPD enrolled in a 12-week community-based PR programme. Anchor and distribution-based methods were used to compute the MCIDs. The anchors explored were the St. George's respiratory questionnaire (SGRQ) and the six-minute walk test (6MWT) using Pearson's correlations. Pooled MCIDs were computed using the arithmetic weighted mean (2/3 anchor, 1/3 distribution-based methods) and reported as absolute and/or percentage of change values.Eighty-nine people with COPD (84% male, 69.9 ± 7.9 years, FEV₁ 49.9 ± 18.9% predicted) were included. No correlations were found between changes in 1RM and the SGRQ neither between changes in HHD and the SGRQ and 6MWT (p > 0.05). Thus, anchor-based methods were used only in the MCID of the 1RM with the 6MWT as the anchor. The pooled MCIDs were 5.7Kg and 26.9% of change for the isotonic quadriceps muscle strength with 1RM and 5.2KgF for isometric quadriceps muscle strength assessed with HHD.The MCIDs found are estimates to improve interpretability of community-based PR effects on quadriceps muscle strength and may contribute to guide interventions.

Neuromuscular electrostimulation as an adjuvant therapy to pulmonary rehabilitation programs in chronic obstructive pulmonary disease

Introduction. Chronic obstructive pulmonary disease (COPD) is commonly associated with a vicious circle of sedentary lifestyle - deconditioning - muscular dysfunction. High-frequency neuromuscular electrostimulation has demonstrated beneficial effects among subjects with muscle weakness. This study aimed to evaluate the benefits of merging pulmonary rehabilitation program (PRP) with neuromuscular electrostimulation in patients with very severe COPD. Material and methods. The study included 38 males with clinically stable COPD, who were divided in 2 groups: group A-19 patients that underwent a PRP of 5 sessions/week for 4 weeks and group B-19 patients that underwent intercostal and lower extremity muscle electrostimulation (5 sessions/week for 4 weeks, 60 min /session) in association with the same type of PRP. Saint Georges’s Respiratory Questionnaire (SGRQ), Modified Medical Research Council (mMRC) dyspnea scale, spirometry, maximal inspiratory pressure (PImax) and maximal expiratory pressure (PEmax), six minutes walking test (6MWT) and bio-electrical impedance were examined before and after the intervention. Results. Electrostimulation applied in group B increased muscle mass (50.15 ± 0.61kg vs 53.97 ± 0.87kg, p<0.001)., PEmax (5.41 ± 0.25 vs post 6.79 ± 0.22, p<0.0003) and improved mMRC score (2.68 ± 0.15 vs 2.10 ± 0.15, p<0.0109), 6MWT (369.6 ± 10.77m vs post: 445.6 ± 6.03 m) and SGRQ (61.32 ± 1.83 vs. 44.95 ± 1.94, p<0.0001). In group B only SGRQ score (55.05 ± 1.32 vs. 50.05 ± 1.51, p=0.018) was improved after PRP. Conclusion. A protocol which combines PRP with neuromuscular electrical stimulation in patients with very severe forms of COPD, has grater beneficial effect on dyspnoea, exercise tolerance, muscle mass toning and quality of life, compared with PRP alone.

Effects of neuromuscular electrical stimulation in patients with pulmonary arterial hypertension: a randomized controlled pilot study

BACKGROUND

Patients with pulmonary arterial hypertension (PAH) present impairments in muscle strength and exercise capacity. There is growing evidence about the benefits of neuromuscular electrical stimulation (NMES) in patients with respiratory diseases, except in patients with PAH. The aim of this study was to investigate the effects of NMES on muscle strength, and other physical and psychosocial variables in patients with PAH.

METHODS

Patients with PAH were randomly divided into two groups as NMES and control. The NMES was applied to the bilateral deltoid and quadriceps femoris muscles with 50 Hz for 3 days/week, 8 weeks for the NMES group. Muscle strength, muscle cross-sectional area and thickness, arterial stiffness, exercise capacity, functional mobility and balance, balance confidence, fatigue, physical activity, and quality of life were assessed at baseline and after 8 weeks by blinded assessors.

RESULTS

There was no significant difference in the demographic and clinical characteristics between the patient groups (p > 0.05). The improvements in muscle strength, muscle cross-sectional area and thickness, pulse wave velocity, exercise capacity, functional mobility and balance, balance confidence, fatigue, physical activity, and quality of life were significantly higher in the NMES group compared to the control group (p < 0.05).

CONCLUSIONS

This study suggests that NMES intervention is safe and effective for patients with PAH.

An update on pulmonary rehabilitation techniques for patients with chronic obstructive pulmonary disease

Introduction: Pulmonary rehabilitation (PR) is one of the core components in the management of patients with chronic obstructive pulmonary disease (COPD). In order to achieve the maximal level of independence, autonomy, and functioning of the patient, targeted therapies and interventions based on the identification of physical, emotional and social traits need to be provided by a dedicated, interdisciplinary PR team.Areas covered: The review discusses cardiopulmonary exercise testing in the selection of different modes of training modalities. Neuromuscular electrical stimulation as well as gait assessment and training are discussed as well as add-on therapies as oxygen, noninvasive ventilator support or endoscopic lung volume reduction in selected patients. The potentials of pulsed inhaled nitric oxide in patients with underlying pulmonary hypertension is explored as well as nutritional support. The impact of sleep quality on outcomes of PR is reviewed.Expert opinion: Individualized, comprehensive intervention based on thorough assessment of physical, emotional, and social traits in COPD patients forms a continuous challenge for health-care professionals and PR organizations in order to dynamically implement and adapt these strategies based on dynamic, more optimal understanding of underlying pathophysiological mechanisms.

Add-on interventions during pulmonary rehabilitation

Both pulmonary rehabilitation (PR) and chronic obstructive pulmonary disease (COPD) are generic terms and it increasingly becomes clear that rehabilitation programmes need to be tailored to the complexity and circumstances of the individual patient. Indeed, PR is described as a comprehensive, individualized intervention based on thorough assessment of identifiable treatable traits. The current review summarizes ongoing developments regarding additional interventions and tools to facilitate PR and improve outcomes in patients with a chronic respiratory disease.

Neuromuscular electrical stimulation improves exercise capacity in adult patients with chronic lung disease: a meta-analysis of English studies

Background

Neuromuscular electrical stimulation (NMES) has been suggested as an alternative rehabilitative therapy to enhance exercise performance and skeletal muscle function in adult patients with chronic lung disease. However, the results of individual studies have been inconsistent. We performed a meta-analysis to evaluate the effectiveness of NMES with regard to increasing exercise capacity, quadriceps strength, muscle mass, cross-sectional area, and quality of life and decreasing dyspnea in adult patients with chronic lung disease.

Methods

A systematic search was conducted of the PubMed, Cochrane Library and EMBASE databases for randomized controlled trials (RCTs) published in English-language journals before January 2018. Data were extracted using standardized forms, and the weighted mean difference (WMD) or standardized mean difference (SMD) with 95% confidence intervals (CIs) was calculated.

Results

Eleven RCTs involving 368 patients were included in this meta-analysis. The pooled results showed that NMES significantly improved the 6-min walk distance (WMD: 37.93 m, 95% CI: 19.53-56.33 m; P<0.0001; P for heterogeneity =0.11; I²=47%) but not the incremental shuttle walk test (WMD: 18.18 m, 95% CI: -79.41 to 115.77 m, P=0.72; P for heterogeneity <0.0001, I²=94%) or endurance shuttle walk test (ESWT) (WMD: 96.73 m, 95% CI: -45.58 to 239.03 m, P=0.18; P heterogeneity =0.22, I²=34%). Moreover, NMES was associated with a significant improvement in quadriceps strength (SMD: 1.14, 95% CI: 0.86-1.43, P<0.00001; P heterogeneity =0.02, I²=58%).

Conclusions

This systemic review and meta-analysis provided evidence supporting the beneficial role of NMES in improving exercise capacity in patients with chronic respiratory disease.

Neuromuscular electrostimulation for adults with chronic obstructive pulmonary disease

BACKGROUND

In people with chronic obstructive pulmonary disease (COPD), the use of neuromuscular electrostimulation (NMES) either alone, or together with conventional exercise training, might improve the condition of the peripheral muscles, increase exercise capacity and functional performance, reduce symptoms and improve health-related quality of life (HRQoL).

OBJECTIVES

To determine the effects of NMES, applied in isolation or concurrently with conventional exercise training to one or more peripheral muscles, on peripheral muscle force and endurance, muscle size, exercise capacity, functional performance, symptoms, HRQoL and adverse events in people with COPD.

SEARCH METHODS

We searched the Cochrane Airways Group Specialised Register, the Physiotherapy Evidence Database, clinical trial registries and conference abstracts on 14 March 2018.

SELECTION CRITERIA

Randomised controlled trials that recruited adults with COPD if they had compared outcomes between a group that received NMES and a group that received usual care or compared outcomes between a group that received NMES plus conventional exercise training and a group that participated in conventional exercise training alone.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data and assessed risk of bias using the Cochrane 'Risk of bias' tool. We expressed continuous data as either the standardised mean difference (SMD) or mean difference (MD) with the corresponding 95% confidence interval (CI). We assessed the quality of evidence using the GRADE approach.

MAIN RESULTS

Nineteen studies met the inclusion criteria of which 16 contributed data on 267 participants with COPD (mean age 56 to 76 years and 67% were men). Of these 16 studies, seven explored the effect of NMES versus usual care and nine explored the effect of NMES plus conventional exercise training versus conventional exercise training alone. Six studies utilised sham stimulation in the control group. When applied in isolation, NMES produced an increase in peripheral muscle force (SMD 0.34, 95% CI 0.02 to 0.65; low-quality evidence) and quadriceps endurance (SMD 1.36, 95% CI 0.59 to 2.12; low-quality evidence) but the effect on thigh muscle size was unclear (MD 0.25, 95% CI -0.11 to 0.61; low-quality evidence). There were increases in six-minute walk distance (6MWD) (MD 39.26 m, 95% CI 16.31 to 62.22; low-quality evidence) and time to symptom limitation exercising at a submaximal intensity (MD 3.62 minutes, 95% CI 2.33 to 4.91). There was a reduction in the severity of leg fatigue on completion of an exercise test (MD -1.12 units, 95% CI -1.81 to -0.43). The increase in peak rate of oxygen uptake (VO_2peak) was of borderline significance (MD 0.10 L/minute, 95% CI 0.00 to 0.19).For NMES with conventional exercise training, there was an uncertain effect on peripheral muscle force (SMD 0.47, 95% CI -0.10 to 1.04; very low-quality evidence) and there were insufficient studies to undertake a meta-analysis on the effect on quadriceps endurance or thigh muscle size. However, there was an increase in 6MWD in favour of NMES combined with conventional exercise training (MD 25.87 m, 95% CI 1.06 to 50.69; very low-quality evidence). In people admitted to either in an intensive care unit or a respiratory high dependency centre, NMES combined with conventional exercise reduced the time taken for participants to first sit out of bed by 4.98 days (95% CI -8.55 to -1.41; very low-quality evidence), although the statistical heterogeneity for this analysis was high (I² = 60%). For both types of studies (i.e. NMES versus usual care and NMES with conventional exercise training versus conventional exercise training alone), there was no risk difference for mortality or minor adverse events in participants who received NMES.

AUTHORS' CONCLUSIONS

NMES, when applied in isolation, increased quadriceps force and endurance, 6MWD and time to symptom limitation exercising at a submaximal intensity, and reduced the severity of leg fatigue on completion of exercise testing. It may increase VO_2peak, but the true effect on this outcome measure could be trivial. However, the quality of evidence was low or very low due to risk of bias within the studies, imprecision of the estimates, small number of studies and inconsistency between the studies. Although there were no additional gains in quadriceps force with NMES plus conventional exercise training, there was evidence of an increase in 6MWD. Further, in people who were the most debilitated, the addition of NMES may have accelerated the achievement of a functional milestone, that is, the first time someone sits out of bed.

Changes in lower limb muscle function and muscle mass following exercise-based interventions in patients with chronic obstructive pulmonary disease: A review of the English-language literature

Chronic obstructive pulmonary disease (COPD) patients often experience lower limb muscle dysfunction and wasting. Exercise-based training has potential to improve muscle function and mass, but literature on this topic is extensive and heterogeneous including numerous interventions and outcome measures. This review uses a detailed systematic approach to investigate the effect of this wide range of exercise-based interventions on muscle function and mass. PUBMED and PEDro databases were searched. In all, 70 studies (n = 2504 COPD patients) that implemented an exercise-based intervention and reported muscle strength, endurance, or mass in clinically stable COPD patients were critically appraised. Aerobic and/or resistance training, high-intensity interval training, electrical or magnetic muscle stimulation, whole-body vibration, and water-based training were investigated. Muscle strength increased in 78%, muscle endurance in 92%, and muscle mass in 88% of the cases where that specific outcome was measured. Despite large heterogeneity in exercise-based interventions and outcome measures used, most exercise-based trials showed improvements in muscle strength, endurance, and mass in COPD patients. Which intervention(s) is (are) best for which subgroup of patients remains currently unknown. Furthermore, this literature review identifies gaps in the current knowledge and generates recommendations for future research to enhance our knowledge on exercise-based interventions in COPD patients.

Effectiveness of neuromuscular electrical stimulation for the rehabilitation of moderate-to-severe COPD: a meta-analysis

PURPOSE

Patients with COPD often experience skeletal muscle dysfunction. For those who are unable or unwilling to undertake physical training, neuromuscular electrical stimulation (NMES) may provide an alternative method of rehabilitation. The purpose of this meta-analysis was to investigate the controversial topic of whether this therapy is effective in patients with moderate-to-severe COPD.

PATIENTS AND METHODS

We pooled data from nine trials published between January 9, 2002 and January 4, 2016 across PubMed, Embase, Cochrane Central Register of Controlled Trials, Google Scholar, and relevant websites for randomized controlled trials. In these trials, patients with moderate-to-severe COPD were randomly allocated to receive NMES. Primary outcomes were quadricep strength and exercise capacity. The secondary outcome was health-related quality of life.

RESULTS

We extracted data from 276 patients. NMES contributed to statistically improved quadricep strength (standardized mean difference 1.12, 95% confidence interval [CI] 0.64-1.59, I²=54%; P<0.00001) and exercise capacity, including longer exercise distance (weighted mean difference 51.53, 95% CI 20.13-82.93, I²=90%; P=0.001), and longer exercise endurance (standardized mean difference 1.11, 95% CI 0.14-2.08, I²=85%; P=0.02). There was no significant difference in St George's Respiratory Questionnaire scores (weighted mean difference -0.07, 95% CI -2.44 to 2.30, I²=56%; P=0.95).

CONCLUSION

NMES appears an effectual means of enhancing quadricep strength and exercise capacity in moderate-to-severe COPD patients. Further research is demanded to clarify its effect on other outcomes and determine the optimal parameters for an NMES program.

Neuromuscular electrical stimulation for muscle weakness in adults with advanced disease

BACKGROUND

This review is an update of a previously published review in the Cochrane Database of Systematic Reviews Issue 1, 2013 on Neuromuscular electrical stimulation for muscle weakness in adults with advanced disease.Patients with advanced progressive disease often experience muscle weakness, which can impact adversely on their ability to be independent and their quality of life. In those patients who are unable or unwilling to undertake whole-body exercise, neuromuscular electrical stimulation (NMES) may be an alternative treatment to enhance lower limb muscle strength. Programmes of NMES appear to be acceptable to patients and have led to improvements in muscle function, exercise capacity, and quality of life. However, estimates regarding the effectiveness of NMES based on individual studies lack power and precision.

OBJECTIVES

Primary objective: to evaluate the effectiveness of NMES on quadriceps muscle strength in adults with advanced disease. Secondary objectives: to examine the safety and acceptability of NMES, and its effect on peripheral muscle function (strength or endurance), muscle mass, exercise capacity, breathlessness, and health-related quality of life.

SEARCH METHODS

We identified studies from searches of the Cochrane Central Register of Controlled Trials (CENTRAL), Cochrane Database of Systematic Reviews (CDSR), and Database of Abstracts of Reviews of Effects (DARE) (the Cochrane Library), MEDLINE (OVID), Embase (OVID), CINAHL (EBSCO), and PsycINFO (OVID) databases to January 2016; citation searches, conference proceedings, and previous systematic reviews.

SELECTION CRITERIA

We included randomised controlled trials in adults with advanced chronic respiratory disease, chronic heart failure, cancer, or HIV/AIDS comparing a programme of NMES as a sole or adjunct intervention to no treatment, placebo NMES, or an active control. We imposed no language restriction.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data on study design, participants, interventions, and outcomes. We assessed risk of bias using the Cochrane 'Risk of bias' tool. We calculated mean differences (MD) or standardised mean differences (SMD) between intervention and control groups for outcomes with sufficient data; for other outcomes we described findings from individual studies. We assessed the evidence using GRADE and created a 'Summary of findings' table.

MAIN RESULTS

Eighteen studies (20 reports) involving a total of 933 participants with COPD, chronic respiratory disease, chronic heart failure, and/or thoracic cancer met the inclusion criteria for this update, an additional seven studies since the previous version of this review. All but one study that compared NMES to resistance training compared a programme of NMES to no treatment or placebo NMES. Most studies were conducted in a single centre and had a risk of bias arising from a lack of participant or assessor blinding and small study size. The quality of the evidence using GRADE comparing NMES to control was low for quadriceps muscle strength, moderate for occurrence of adverse events, and very low to low for all other secondary outcomes. We downgraded the quality of evidence ratings predominantly due to inconsistency among study findings and imprecision regarding estimates of effect. The included studies reported no serious adverse events and a low incidence of muscle soreness following NMES.NMES led to a statistically significant improvement in quadriceps muscle strength as compared to the control (12 studies; 781 participants; SMD 0.53, 95% confidence interval (CI) 0.19 to 0.87), equating to a difference of approximately 1.1 kg. An increase in muscle mass was also observed following NMES, though the observable effect appeared dependent on the assessment modality used (eight studies, 314 participants). Across tests of exercise performance, mean differences compared to control were statistically significant for the 6-minute walk test (seven studies; 317 participants; 35 m, 95% CI 14 to 56), but not for the incremental shuttle walk test (three studies; 434 participants; 9 m, 95% CI -35 to 52), endurance shuttle walk test (four studies; 452 participants; 64 m, 95% CI -18 to 146), or for cardiopulmonary exercise testing with cycle ergometry (six studies; 141 participants; 45 mL/minute, 95% CI -7 to 97). Limited data were available for other secondary outcomes, and we could not determine the most beneficial type of NMES programme.

AUTHORS' CONCLUSIONS

The overall conclusions have not changed from the last publication of this review, although we have included more data, new analyses, and an assessment of the quality of the evidence using the GRADE approach. NMES may be an effective treatment for muscle weakness in adults with advanced progressive disease, and could be considered as an exercise treatment for use within rehabilitation programmes. Further research is very likely to have an important impact on our confidence in the estimate of effect and may change the estimate. We recommend further research to understand the role of NMES as a component of, and in relation to, existing rehabilitation approaches. For example, studies may consider examining NMES as an adjuvant treatment to enhance the strengthening effect of programmes, or support patients with muscle weakness who have difficulty engaging with existing services.

Neuromuscular electrical stimulation to improve exercise capacity in patients with severe COPD: a randomised double-blind, placebo-controlled trial

BACKGROUND

Skeletal muscle dysfunction and exercise intolerance are common in severe chronic obstructive pulmonary disease (COPD). We assessed the effectiveness of neuromuscular electrical stimulation (NMES) as a home-based exercise therapy.

METHODS

In this double-blind, placebo-controlled trial, undertaken across three UK National Health Service sites, we randomly assigned (1:1) adults with COPD, a forced expiratory volume in 1 s (FEV1) less than 50% predicted, and incapacitating breathlessness (Medical Research Council dyspnoea scale ≥4) to receive active or placebo NMES, daily over a 6-week period. Randomisation was by an independent system using minimisation to balance age, GOLD stage, and quadriceps strength. Participants and outcome assessors were masked to group allocation. The primary endpoint was change in 6-min walk test (6MWT) distance at 6 weeks. Analysis was by intention to treat. The trial was registered as ISRCTN15985261 and is now closed.

FINDINGS

Between June 29, 2012, and July 4, 2014, we enrolled 73 participants, of whom 52 participants were randomly assigned; 25 to receive active NMES and 27 to placebo NMES. Change in 6MWT distance was greater in the active NMES group (mean 29·9 [95% CI 8·9 to 51·0]) compared with in the placebo group (-5·7 [-19·9 to 8·4]; mean difference at 6 weeks 35·7 m [95% CI 10·5 to 60·9]; p=0·005). Sensitivity analyses for complete-cases and adjustment for baseline values showed similar results. 6 weeks after stopping the intervention the effect waned (7·3 m [95% CI -32·5 to 47·0]; p=0·50). The proportion of participants who had adverse events was similar between groups (five [20%] in the active NMES group and nine [33%] in the placebo group). Two participants, one from each group, reported persistent erythema, which was considered to be possibly related to NMES and the use of adhesive electrodes.

INTERPRETATION

NMES improves functional exercise capacity in patients with severe COPD by enhancing quadriceps muscle mass and function. These data support the use of NMES in the management of patients unable to engage with conventional pulmonary rehabilitation. More work is needed to study how to maintain the effect.

FUNDING

National Institute for Health Research.