Jornal Brasileiro de Pneumologia
Print version ISSN 1806-3713
MULLER, Paulo de Tarso Guerrero; VIEGAS, Carlos Alberto de Assis and PATUSCO, Luiz Armando Pereira. Muscle strength as a determinant of oxygen uptake efficiency and maximal metabolic response in patients with mild-to-moderate COPD. J. bras. pneumol. [online]. 2012, vol.38, n.5, pp. 541-549. ISSN 1806-3713. http://dx.doi.org/10.1590/S1806-37132012000500002.
OBJECTIVE: To compare the behavior of the oxygen uptake efficiency slope (OUES) with that of oxygen uptake at peak exertion (VO2peak). METHODS: This was a prospective cross-sectional study involving 21 patients (15 men) with mild-to-moderate COPD undergoing spirometry, handgrip strength (HGS) testing, cardiopulmonary exercise testing, and determination of lactate at peak exertion (LACpeak). RESULTS: Mean weight was 66.7 ± 13.6 kg, and mean age was 60.7 ± 7.8 years. With the exception of FEV1 and FEV1/FVC ratio (75.8 ± 18.6 of predicted and 56.6 ± 8.8, respectively), all spirometric variables were normal, as was HGS. The patients exhibited significant metabolic and hemodynamic stress, as evidenced by the means (% of predicted) for VO2peak (93.1 ± 15.4), maximum HR (92.5 ± 10.4), and OUES (99.4 ± 24.4), as well as for the gas exchange rate (1.2 ± 0.1). The correlation between VO2peak and OUES was significant (r = 0.747; p < 0.0001). The correlation between HGS and VO2peak (r = 0.734; p < 0.0001) was more significant than was that between HGS and OUES (r = 0.453; p < 0.05). Similar results were found regarding the correlations of VO2peak and OUES with MIP. Although LACpeak correlated significantly with VO2peak (r = -0.731; p < 0.0001), only LACpeak/maximum power correlated significantly with OUES (r = -0.605; p = 0.004). CONCLUSIONS: Our findings suggest that, in mild-to-moderate COPD, VO2 determinants other than overall muscle strength have a greater impact on OUES than on VO2peak.
Keywords : Respiratory function tests; Pulmonary disease; chronic obstructive; Muscle strength; Oxygen consumption.