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Stimulating Advances in Chronic Heart Failure and COPD

2009; Elsevier BV; Volume: 136; Issue: 1 Linguagem: Inglês

10.1378/chest.09-0408

1931-3543

Isabelle Vivodtzev, Yves Lacasse,

Cardiovascular and exercise physiology

In some patients with chronic heart failure (CHF) and COPD, physical deconditioning may be so severe that exercise training cannot be initiated. This situation has encouraged the investigation of “local muscle training” by neuromuscular electrical stimulation (NMES) of the lower limbs. In this issue of CHEST (see page 44), Sillen et al1Sillen MJH Speksnijder CM Eterman R-MA et al.Effects of neuromuscular electrical stimulation of muscles of ambulation in patients with CHF or COPD: a systematic review of the English-language literature.Chest. 2009; 136: 44-61Abstract Full Text Full Text PDF PubMed Scopus (144) Google Scholar summarize the best available evidence from the English-language literature to demonstrate the potential of NMES training vs no training or sham stimulation to improve muscle function and quality of life in patients with CHF and COPD. We are aware of at least one other randomized trial2Hoomans N Pneumologie, soins intensifs: amélioration de la qualité de vie des insuffisants respiratoires chroniques obstructifs sévères; renforcement des quadriceps par électrostimulation.Kinesither Sci. 2004; 440: 47-48Google Scholar published in a “foreign” language that suggested similar improvements in walking distance and muscle strength after training in both NMES and voluntary contractions among patients with COPD and respiratory failure. Sillen et al1Sillen MJH Speksnijder CM Eterman R-MA et al.Effects of neuromuscular electrical stimulation of muscles of ambulation in patients with CHF or COPD: a systematic review of the English-language literature.Chest. 2009; 136: 44-61Abstract Full Text Full Text PDF PubMed Scopus (144) Google Scholar did not proceed with a metaanalysis of the available data, arguing that heterogeneity existed across trials. We would certainly agree with this decision that does not diminish the interest of this systematic review. In summary, the benefits observed after NMES training in CHF patients were comparable to those reported in COPD patients and consisted of improvements in muscle strength, exercise capacity, and, when measured, health-related quality of life. In addition, studies in CHF patients3Deley G Kervio G Verges B et al.Comparison of low-frequency electrical myostimulation and conventional aerobic exercise training in patients with chronic heart failure.Eur J Cardiovasc Prev Rehabil. 2005; 12: 226-233Crossref PubMed Scopus (0) Google Scholar have shown enhanced maximal aerobic capacity after NMES to the same extent as that observed after endurance training. Other studies included in the systematic review suggested that muscle proteins4Nuhr MJ Pette D Berger R et al.Beneficial effects of chronic low-frequency stimulation of thigh muscles in patients with advanced chronic heart failure.Eur Heart J. 2004; 25: 136-143Crossref PubMed Scopus (162) Google Scholar and vascular adaptations5Karavidas AI Raisakis KG Parissis JT et al.Functional electrical stimulation improves endothelial function and reduces peripheral immune responses in patients with chronic heart failure.Eur J Cardiovasc Prev Rehabil. 2006; 13: 592-597Crossref PubMed Scopus (71) Google Scholar may be potential mechanisms of improvement after NMES training in CHF patients. The mechanisms of NMES are still poorly understood, however. Studies in COPD and CHF patients have primarily focused on the benefits of NMES training even before describing its short-term effects. Although the use of NMES is mainly based on a suggested minimal impact on ventilation (or dyspnea), only one recent study6Sillen MJ Janssen PP Akkermans MA et al.The metabolic response during resistance training and neuromuscular electrical stimulation (NMES) in patients with COPD, a pilot study.Respir Med. 2008; 102: 786-789Abstract Full Text Full Text PDF PubMed Scopus (62) Google Scholar has described the cardiorespiratory response to it (in comparison with voluntary contractions), and no study has measured exercise-induced muscle fatigue after NMES. Such investigations are further complicated by important individual variations in the capacity to produce and tolerate a muscle contraction for a given intensity of electrical stimulation.7Lloyd T De Domenico G Strauss GR et al.A review of the use of electro-motor stimulation in human muscles.Aust J Physiother. 1986; 32: 18-30Abstract Full Text PDF PubMed Scopus (44) Google Scholar, 8Lieber RL Kelly MJ Factors influencing quadriceps femoris muscle torque using transcutaneous neuromuscular electrical stimulation.Phys Ther. 1991; 71: 715-721Crossref PubMed Scopus (57) Google Scholar Physical composition, dyspnea and leg discomfort during NMES, inflammation, and muscle fatigue induced by NMES may influence tolerance to NMES.8Lieber RL Kelly MJ Factors influencing quadriceps femoris muscle torque using transcutaneous neuromuscular electrical stimulation.Phys Ther. 1991; 71: 715-721Crossref PubMed Scopus (57) Google Scholar It is therefore no surprise that the techniques of NMES have varied widely in the randomized trials that met the inclusion criteria of the systematic review. Different responses may be obtained from different stimulation frequencies, amplitudes, and duty cycles (ie, the ratio of contraction to [contraction + rest] durations).9Vivodtzev I Lacasse Y Maltais F Neuromuscular electrical stimulation of the lower limbs in patients with chronic obstructive pulmonary disease.J Cardiopulm Rehabil Prev. 2008; 28: 79-91Crossref PubMed Scopus (73) Google Scholar For instance, although stimulation of low frequency (1 to 10 Hz) is easy to sustain and produces less fatigue than that of higher frequency, it is agreed that it will produce low force levels in the human quadriceps femoris musculature. High frequencies (40 to100 Hz) are required to induce tetanic muscle contraction in order to recruit a large number of muscular units10Roos MR Rice CL Connelly DM et al.Quadriceps muscle strength, contractile properties, and motor unit firing rates in young and old men.Muscle Nerve. 1999; 22: 1094-1103Crossref PubMed Scopus (213) Google Scholar and to produce maximum force.11Binder-Macleod SA McDermond LR Changes in the force-frequency relationship of the human quadriceps femoris muscle following electrically and voluntarily induced fatigue.Phys Ther. 1992; 72: 95-104Crossref PubMed Scopus (79) Google Scholar Similarly, the optimal duty cycle is unknown, with a proposed range varying between 10% and 50%.12Packman-Braun R Relationship between functional electrical stimulation duty cycle and fatigue in wrist extensor muscles of patients with hemiparesis.Phys Ther. 1988; 68: 51-56Crossref PubMed Scopus (52) Google Scholar The addition of small differences in any of these parameters ends up resulting in heterogeneity in the intervention across trials. The standardization of NMES parameters would facilitate between-studies comparisons. Who are the patients most likely to benefit from NMES? From the published studies,9Vivodtzev I Lacasse Y Maltais F Neuromuscular electrical stimulation of the lower limbs in patients with chronic obstructive pulmonary disease.J Cardiopulm Rehabil Prev. 2008; 28: 79-91Crossref PubMed Scopus (73) Google Scholar an emerging concept is that NMES may be particularly effective and useful in patients with advanced disease as opposed to those with earlier stages of disease. NMES is not a panacea, however. NMES is definitely not an alternative to exercise training in patients who are able to voluntarily exercise. Rather, a better utilization of NMES would be as an adjunct to exercise training. Also, NMES may be used in patients with severe muscular deconditioning as a bridge between the hospital bed and the rehabilitation unit where exercise training takes place. Another potential utilization of NMES would be immediately after an acute exacerbation of COPD or an episode of acute heart failure to avoid muscle loss and reduction in functional capacities. Further studies are needed to identify the physiologic mechanisms of improvements after NMES, the optimal parameters of stimulation and its indications. The systematic review by Sillen et al1Sillen MJH Speksnijder CM Eterman R-MA et al.Effects of neuromuscular electrical stimulation of muscles of ambulation in patients with CHF or COPD: a systematic review of the English-language literature.Chest. 2009; 136: 44-61Abstract Full Text Full Text PDF PubMed Scopus (144) Google Scholar includes 14 randomized trials (CHF, 9 patients; COPD, 5 patients) involving 365 patients (CHF, 274 patients; COPD, 91 patients). Larger multicenter, randomized trials will be necessary before recommending the widespread use of this treatment modality in CHF and COPD patients.