PURPOSE: Patients with COPD have limited exercise capacity. The role of respiratory and peripheral muscle in this limitation is unclear. The aim of this study was to explore the relation between muscular function with exercise capacity in COPD.
METHODS: We studied 116 patients with COPD who completed PFTs, a cardiopulmonary exercise test as well as a six minutes walk test (6 MWD). The parameters considered as markers of muscular performance were: Fat Free Mass (FFM), Fat Free Mass Index (FFMI), PImax, PEmax, Maximal Voluntary Ventilation (MVV) and Hand grip force. We then evaluated the strength of the association between the different variables and exercise capacity.
RESULTS: The mean age of the 41 men and 75 women with COPD was 65 ± 9 years, BMI 27 ± 5 kg/m2, FFM 57 ± 14 kg, FFMI 20 ± 4 kg/m2, FEV1 37 ± 12%, PImax 66 ± 27 cmH2O, PEmax 97 ± 38 cmH2O, MVV 42 ± 18 L, hand grip force 32 ± 11 kg. The exercise capacity was: Max VO2 0.9 ± 0.4 L, Max VO2 50 ± 20%, 6 MWD 398 m ± 118. The VO2 max % was associated with: PImax (r = 0.26, p = 0.008) and MVV (r = 0.55, p < 0.001), whereas the 6 MWD was associated with: PImax (r = 0.42, p < 0.001), MVV (r = 0.63, p< 0.0001) and hand grip force (r = 0.34, p = 0.0003).
CONCLUSION: Two respiratory muscles function parameters (PImax, MVV) are associated with both maximal and sub-maximal exercise capacity. Hand grip force, as a marker of peripheral muscle strength, is also related with six minutes walked distance.
CLINICAL IMPLICATIONS: Improvement of respiratory peripheral muscle strength might increase exercise capacity in patients with COPD.
DISCLOSURE: Felipe Cortopassi, None.