Muscular Dysfunction in COPD: Systemic Effect or Deconditioning?

BACKGROUND

Muscular dysfunction has been described as one of the systemic manifestations of chronic obstructive pulmonary disease (COPD).

OBJECTIVE

The aim of this study was to evaluate muscular strength of the different anatomical compartments in patients with severe COPD compared with healthy controls.

METHOD

We performed a cross-sectional study in patients with severe COPD. We evaluated the muscular strength of the respiratory muscles, flexors and extensors of the cervical spine and knee, as well as handgrip force. The 6-min walking test (6MWT) and serum inflammatory markers were also analysed.

RESULTS

Twenty-eight male patients with COPD (mean age 67.8 years, mean FEV1 (%) 39 %) and 24 male healthy controls (mean age 70.2 years) were studied. The strength of the flexors and extensors of the knee was significantly reduced in patients with COPD (p < 0.001 and p = 0.003). No differences were observed in the flexors and extensors of the cervical spine and handgrip force between groups. No correlation was observed between the muscular strength in the different anatomic compartments and the concentrations of blood inflammatory biomarkers or the metres walked in the 6MWT in COPD patients. However, a significant negative linear correlation was observed between the 6MWT and IL-6 and IL-8 levels (rho = -0.67, p = 0.001; rho = -0.57, p = 0.008). In addition, we found a negative correlation between the 6MWT and inspiratory capacity (rho = -0.755, p = 0.031).

CONCLUSIONS

Our results suggest that muscular dysfunction in patients with COPD differs in different muscular compartments. The main factor for a reduced exercise capacity was a reduction in inspiratory capacity.