Neuromuscular electrical stimulation appears to be useful in people with severe chronic obstructive pulmonary disease

Blikk på forskning i Fysioterapeuten 2/2013

Fagartikkel

Blikk på forskning utarbeides i samarbeid med Journal of Physiotherapy (Australia), som trykker forskningspresentasjonene under betegnelsen Critically appraised Papers, CAPs.

Synopsis

Summary of: Vivodtzev I et al (2012) Functional and muscular effects of neuromuscular electrical stimulation in patients with severe COPD: a randomised clinical trial.Chest141: 716–725. [Prepared by Kylie Hill, CAP Editor.]

Question: In patients with chronic obstructive pulmonary disease (COPD), what effect does neuromuscular electrical stimulation (NMES) have on muscle function and walking endurance?

Design: Randomised, controlled trial in which the patients and those who collected outcome measures were blinded to group allocation.

Setting: Home-based intervention with outcomes collected at a hospital in Quebec City, Canada.Participants: Patients who were clinically stable, sedentary and able to travel to the hospital with: (a) a smoking history > 20 pack-years, (b) severe airflow obstruction, and (c) a 6-minute walk distance < 400 m. Exclusion criteria comprised any co-morbid condition associated with muscle wasting. Randomisation of 22 patients allocated 13 to the intervention group and 9 to the control group.Interventions: Both groups received electrical stimulation 5 times a week for 6 weeks. Each session comprised 35 min of bilateral stimulation for the quadriceps and 25 min of bilateral stimulation for the calf. Stimulation was applied with the patient in sitting. They were encouraged to increase the intensity to the maximum they could tolerate. Patients were visited weekly at home by a research nurse to monitor progress. Parameters used by the intervention group were 50 Hz frequency, 400 μs pulse duration, and 6 sec/16 sec duty cycle. Parameters used by the control/sham group were 5 Hz frequency, 100 μs pulse duration, applied continuously.
Outcome measures: The primary outcome was quadriceps strength. The secondary outcomes included quadriceps endurance and performance during the endurance shuttle walk test.

Results: Data were available on 12 and 8 patients in the intervention and control groups, respectively. Current intensity increased over the training period in the intervention group from 20 ± 4 mA to 31 ± 10 mA (p< 0.001). Compared with the control group, the intervention group conferred greater gains in quadriceps force (difference in mean percent change from baseline 14%, 95% CI 1% to 26%) and endurance (42%, 95% CI 4% to 80%), but not walking endurance.

Conclusion: In patients with severe COPD, NMES delivered at home enhanced muscle function but not walking endurance.

[95% CIs provided by primary author on request]

Commentary

Neuromuscular electrical stimulation (NMES) has increasingly been used in patients with chronic heart failure and chronic obstructive pulmonary disease with or without volitional exercise (Sillen et al 2009) and more recently in critically ill patients (Gerovasili et al 2009a). This well-designed, randomised study addressed some of the issues raised by the heterogeneity of NMES protocols and elucidated the mechanisms involved in the changes in muscle function. Despite the small sample size, this study carries some important clinical messages. First, the effectiveness was proportional to current intensity, which is clinically relevant when selecting patients for NMES. Namely, patients unable to tolerate progression of current intensity seem unlikely to benefit from NMES when prescribed as a home-based rehabilitation modality. Second, between-group differences in exercise capacity were not demonstrated. This may relate to a methodological issue; that is the authors opted for lowexercise intensityby stimulating the thigh and calf muscles consecutively rather than simultaneously.

The systemic effect of NMES, as previously shown (Gerovasili et al 2009b), is dependent on stimulating adequate muscle bulk, which the authors may have better achieved by simultaneously stimulating all muscle groups. Finally, the authors assessed the mechanisms involved in the improvement of muscle function, which was partially attributed to muscle hypertrophy and restoration of the anabolic/catabolic balance, although other mechanisms such as the role of microcirculation and neural adaptation are possible contributors. NMES is an effective exercise modality for patients with severe COPD. Protocol and exercise intensity are relevant to induced changes in muscle function, which physiotherapists should take into account. Patients intolerant of progression of current intensity should be considered for supervised sessions.

Vasiliki Gerovasili

First Critical Care Department, National and Kapodistrian University of Athens, Greece.

References

Gerovasili V et al (2009a)Crit Care13: R161.

Gerovasili V et al (2009b)Chest136: 1249–1256.

Sillen MJH et al (2009)Chest136: 44–61.

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