Does muscle wasting always mean muscle weakness? A prevalence study in COPD

Le résumé fourni par la source

Peripheral muscle mass and strength are relevant indicators of COPD survival. Current guidelines recommend to assess muscle strength only in muscle wasted patients. However, a recent study reported quadriceps weakness without muscle wasting (Menon, M et al . Resp. Res.2012, 13:119). Thus, these guidelines raise the risk to miss out some weak patients. In clinical settings, fat-free-mass index (FFMI) is indicated as a simple index to assess muscle wasting. We aimed at determining the prevalence of patients entering in pulmonary rehabilitation (PR) a priori not eligible for muscle strength evaluation given the lack of muscle wasting clinical signs. FFMI and Quadriceps strength (QMVC) were assessed in 138 COPD patients (FEV1=52±24%). In absence of consensus, we used the criteria of Seymour, JM. et al . (ERJ.2010,36(1):81–88), ie muscle wasting =FFMI<10th percentile and muscle weakness =((obs.-pred. QMVC)/8.58)<-1.645. 52% of patients (n=72) had no muscle wasting. Among them, 47% (n=34) had muscle weakness ie 25% of the total sample. Surprisingly, among the 48% (n=66) of muscle wasted patients, 55% (n=36) exhibited normal strength. Beyond the fact that clinical tools and criteria of muscle evaluation should be clearly defined, our results reveal that half of weak patients had no muscle wasting. Thus, structure and function should not be considered as 2 necessarily dependent parameters. Hence, we propose to evaluate both parameters in all patients before RP to ensure the best patient management taking into account their real needs concerning both muscle weakness and wasting. Furthermore, the absence of muscle weakness in some muscle wasted patients also suggests the existence of compensatory neuromuscular mechanisms.

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