Jornal Brasileiro de Pneumologia (Oct 2012)
Força muscular como determinante da eficiência do consumo de oxigênio e da máxima resposta metabólica ao exercício em pacientes com DPOC leve/moderada Muscle strength as a determinant of oxygen uptake efficiency and maximal metabolic response in patients with mild-to-moderate COPD
Abstract
OBJETIVO: Comparar o comportamento de oxygen uptake efficiency slope (OUES, inclinação da eficiência do consumo de oxigênio) com o do consumo de oxigênio no pico do exercício (VO2pico). MÉTODOS: Estudo prospectivo transversal envolvendo 21 pacientes (15 homens) com DPOC leve/moderada que foram submetidos a espirometria, dinamometria de preensão palmar (DIN), teste cardiopulmonar de exercício e medida de lactato no pico do exercício (LACpico). RESULTADOS: A média de peso foi 66,7 ± 13,6 kg, e a de idade foi 60,7 ± 7,8 anos. Com exceção de VEF1 e relação VEF1/CVF (75,8 ± 18,6 do previsto e 56,6 ± 8,8, respectivamente), as demais variáveis espirométricas foram normais, assim como DIN. As médias, em % do previsto, para VO2pico (93,1 ± 15,4), FC máxima (92,5 ± 10,4) e OUES (99,4 ± 24,4), assim como a da taxa de troca respiratória (1,2 ± 0,1), indicaram estresse metabólico e hemodinâmico importante. A correlação entre o VO2pico e a OUES foi elevada (r = 0,747; p 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.
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