Lack of efficacy of neuromuscular electrical stimulation of the lower limbs in chronic obstructive pulmonary disease patients: a meta-analysis.

Randomized controlled trials (RCT) were carried out to investigate the role of neuromuscular electrical stimulation (NMES) in patients with chronic obstructive pulmonary disease (COPD). However, these studies have small sample size and different measures for evaluating outcomes, and convey inconclusive results. We carried out a meta-analysis to assess the effects of NMES to COPD patients. A computerized search was performed through PubMed and Embase databases (up to December 2012) for relevant RCT. Two investigators independently screened the articles. The primary outcome measures were quadriceps strength and exercise capacity, secondary outcomes included dyspnoea and muscle fibre characteristics. The weighted mean difference (WMD) or standardized mean difference and the 95% confidence interval (CI) were calculated, and the heterogeneity was assessed with the I(2) test. Eight trials involving 156 patients were included in this meta-analysis. We found that NMES was not associated with significant changes in quadriceps strength (standardized mean difference 0.38; 95% CI: -0.13-0.89) nor 6 min walk distance (WMD 13.63 m; 95% CI: -17.39-44.65). NMES failed to improve the muscle fibre characteristics (type I: WMD 1.09%; 95% CI: -19.45-21.64; type IIa: WMD -7.50%; 95% CI: -19.81-4.81). NMES significantly improved dyspnoea (WMD -0.98 scores; 95% CI: -1.42- -0.54). Evidence to support the benefits of NMES to COPD patients is currently inadequate. Larger-scale studies are needed to investigate the efficacy of NMES.