COPD patients' oxygen uptake and heart rate on-kinetics at cycle-ergometer: correlation with their predictors of severity

OBJECTIVES: To assess whether there is a correlation between oxygen uptake (VO2) and heart rate (HR) on-kinetics in the constant-load cycle-ergometer test (CLT) and the BODE index and its isolated variables in patients with chronic obstructive pulmonary disease (COPD). METHOD: Fourteen male patients between 55 and 78 years of age with moderate to severe COPD were evaluated. Each patient underwent spirometry, the six-minute walk test (6MWT), the cycle-ergometer incremental test (IT) and CLT on alternate days. The exhaled gases were collected, and the VO2 and HR on-kinetics were analyzed. The BODE index was calculated. RESULTS: It was noted that the VO2 tau (τ) and mean response time (MRT) were significantly higher than HR τ and MRT. Moderate and strong correlations between τ and MRT of the VO2 and HR and the BODE index was noted (r=0.75 and r=0.78; r=0.62 and r=0.63, respectively), and there were correlations between the VO2 τ and MRT and the forced expiratory volume in one second (FEV1) (r=-0.60; r=-0.53) and the distance traveled at 6MWT (DT-6MWT) (r=-0.61; r=-0.44) and DT-6MWT % predicted (r=-0.62; r=-0.46). The HR τ and MRT were correlated with DT-6MWT (r=-0.59; r=-0.58) and DT-6MWT % predicted (r=-0.62; r=-0.62). CONCLUSION: The slowing of cycle-ergometer VO2, and especially of HR on-kinetics, may be key markers of disease severity. Furthermore, airflow obstruction and reduced exercise capacity are associated with the slowing of patients' VO2 and HR on-kinetics. OBJETIVOS: Verificar se há correla o entre a cinética-on do consumo de oxigênio (VO2) e da frequência cardíaca (FC) no teste de carga constante em cicloerg metro (TCC) com o índice BODE e suas variáveis isoladas em pacientes com doen a pulmonar obstrutiva cr nica (DPOC). MéTODO: Foram avaliados 14 homens com DPOC de obstru o moderada a muito grave, entre 55 e 78 anos, submetidos em dias alternados à espirometria, teste de caminhada de seis minutos (TC6), teste incremental em cicloerg metro (TI) e TCC. Foram coletados os gases expirados, e a cinética-on do VO2 e da FC foi analisada. O índice BODE foi calculado. RESULTADOS: Observou-se que a tau (τ) e o tempo de resposta média (TRM) do VO2 foram significativamente maiores que a τ e o TRM da FC. Observou-se correla es moderadas e fortes entre a τ e o TRM do VO2 e da FC com o índice BODE (r=0,75 e r=0,78; r=0,62 e r=0,63, respectivamente) e correla es entre a τ e o TRM do VO2 com o volume expiratório for ado no primeiro segundo (VEF1) (r=-0,60; r=-0,53), a distancia percorrida no TC6 (DP-TC6) (r=-0,61; r=-0,44) e a DP-TC6 %prevista (r=-0,62;