High vs low-frequency neuromuscular electrical stimulation in COPD patients: What happens when current quantity is matched?

Résumé fourni par la source

If the clinical relevance of alternative techniques, such as neuromuscular electrical stimulation (NMES) seems justified in the management of severe COPD patients, no consensus on the parameters of stimulation are clearly given. A recent study showed that high frequencies [HF] increased more muscle strength than low frequencies [LF], but with higher delivered current quantity (same duration of session but higher number of pulses; Sillen et al. Thorax. 2014 0:1-7). We aim at comparing the effects on exercise tolerance and muscle function of two NMES programs [HF] vs [LF] when the quantity of current delivered is identical. 10 COPD patients admitted for pulmonary rehabilitation program (PR) were randomized in two groups: NMES-LF (25Hz, n=4) and NMES-HF (75Hz, n=6). The 2 programs were comparable for all stimulation parameters, excepted for the duration of session that was adjusted to ensure the same quantity of delivered current (LF=30min and HF=10min, 5x/week for 4 weeks). Exercise tolerance (6MWT) and quadriceps torque (Q MVC ) were evaluated before and after PR. 6MWT distance and Q MVC increased significantly after NMES in both groups (p<0.05). However, this increase was not significantly different according to the stimulation frequency used (p interaction ranged from 0.48 to 0.9). The results show that for equivalent amount of delivered current, improvement of exercise tolerance and Q MVC are comparable. The differential effects observed in different programs of NMES thus depends more on the amount of current than the frequency used. Hence, when PR aiming at improving strength, HF may be preferentially proposed because of the shorter duration of session.

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