Muscle Dysfunction, which Impact on Exercise Tolerance and Quality of Life in COPD Patients?

Introduction: COPD is currently considered a real systemic disease due to the concomitant presence of several comorbidities, including peripheral muscle dysfunction, which arises from the interaction of several factors such as undernutrition, inactivity, and systemic inflammation.

Method: To evaluate their muscle dysfunction, stable COPD patients underwent body composition assessment using bioelectrical impedance (BIA), isometric voluntary contraction (MVC) and quadriceps endurance measurement of the lower limb. Patients' exercise tolerance was assessed by the 6-min walk test (6WT), dyspnoea by the m MRC scale and quality of life by the Q11 questionnaire. The aim of our study is to assess the prevalence of muscle dysfunction in COPD patients and to identify its relationship with the severity of bronchial obstruction, as well as its impact on effort tolerance and quality of life in these patients.

Results: 175 COPD patients (166 men and 9 women) aged 67(+/-9) years were recruited, smoking was estimated at 35 (20) p/year, FEV1 averaged 52 (21) %, BMI was 21.32 (4.10) Kg/m2, while FFMI was estimated at 18(4.7) (Kg/m2). Dyspnea was estimated at 2±1 of the m MRC scale. 64% of COPD patients showed muscle weakness with isometric voluntary contraction (MVC) below 80% of normal. Decreased muscle strength was found at all stages of COPD with 13% (GOLD I), 30% (GOLD II), 37% (GOLD III), 20% (GOLD IV). 75% of COPD patients with muscle weakness had dyspnea at stages ≥ 2 m MRC. A significant correlation of quadriceps (MVC) was found with FFMI (p<0.016) and FEV1 (p<0.014). Whereas quadriceps endurance correlated with FEV1 (P<0.0001) and 6-minute walk distance (P<0.0001).