Peripheral Oxidative Stress Markers and Six Minutes Walking Test Performance in COPD Patients

Abstract

Oxidative stress (OS) is involved in the skeletal muscle dysfunction observed in patients with severe chronic obstructive pulmonary disease (COPD). The exercise capacity of these patients can be evaluated measuring the distance that they are able to walk during 6 minutes (six-minute walk test; 6MWT). The systemic inflammation and oxidative stress are potential mechanisms for muscle wasting in COPD patients and 6MWT has been suggested as simple and valid exercise test. PURPOSE: To evaluate the influence of oxidative stress on exercise performance, heart rate (HR), respiratory rate (RR), saturation of peripheral oxygen (SpO2) and Borg modified scale responses to 6MWT in COPD and healthy subjects (HS). METHODS: eighteen COPD patients (64 ± 10 years) and 18 healthy subjects (58 ± 8 years). The patients were selected on the basis of moderate-to-severe COPD according to Global Initiative for Chronic Obstructive Lung Disease (GOLD). Peripheral OS was evalueted in erythrocytes through catalase (CAT) and glutathione s-transferase (GST) antioxidants enzymes activity, and lipid peroxidation (LPO) through chemilumenscence techinic (CL). Exercise performance was evaluated trhough 6MWT (American Thoracic Society). The one way ANOVA and Pearson's correlation test was used (SPSS statistical software). RESULTS: Data showed signifficant difference in HR, RR, SpO2 and Borg scale before and after 6MWT between the two groups. The resting HR values (bpm) were 86 ± 18 and 73 ± 11, and after exercise were 95 ± 20 and 112 ± 16, the resting RR values (vpm) were 21 ± 5 and 16 ± 3, and after exercise were 25 ± 5 and 19 ± 4, the resting SpO2 values were 95 ± 3 and 97 ± 1, and after exercise were 92 ± 7 and 97 ± 1, and the 6MWT values (meters) were 374 ± 100 and 581 ± 52 in COPD and HS, respectively. Data showed no correlation between the distance performed at 6MWT and CAT, GST and CL in both groups. However, the CPOD performed a less distance in 6MWT (p<0,0001). COPD patients reported higher values in Borg scale before and after exercise. There was no difference in OS parameters between the two groups. CONCLUSION: Our data suggest that COPD can influence some cardiorespiratory parameters at resting and after exercise. Moreover, on this presented study, COPD does not alter peripheral OS, and the OS parameters do not influence the exercise performance.