[Association of oxygen uptake efficiency in exercise test with exercise capacity in patients with stable chronic obstructive pulmonary disease].

ABSTRACT

OBJECTIVE: To explore the characteristics of oxygen uptake efficiency (OUE) in patients with chronic obstructive pulmonary disease (COPD), and to analyze the relationship between OUE and the exercise capacity. METHODS: Pulmonary function test and cardiopulmonary exercise test were performed in 59 patients with stable COPD (grade I, n = 15; grade II, n = 16; grade III, n = 19; grade IV, n = 9) and 29 healthy volunteers of the same age. Their successive breathing respiratory exchange parameters were collected and analyzed. t test and χ(2) test were used for 2 sample comparison, while multiple comparisons among groups were performed by using single factor analysis of variance. Correlation analysis was done by Pearson correlation test. RESULTS: Compared with the normal control group [(2.2 ± 0.4) L·min(-1)·lg(L·min(-1))(-1); (35 ± 4) ml/L], the OUES and OUEP of the COPD patient group [(1.9 ± 0.3) L·min(-1)·lg(L·min(-1))(-1); (31 ± 5) ml/L]were significantly lower (t = 4.57, 3.39, all P < 0.01) . The OUE of the grade I patients showed no significant difference compared with the normal control group (t = 0.36-1.49, all P > 0.05), while the OUES of the grade II-IV patients [(2.05 ± 0.26), (1.76 ± 0.28) and (1.63 ± 0.19) L·min(-1)·lg(L·min(-1))(-1)] decreased significantly compared to the normal control group [(2.23 ± 0.39) L·min(-1)·lg(L·min(-1))(-1); t = 2.42-5.26, all P < 0.05]. The OUEP and the OUE at the anaerobic threshold of the grade II-III patients [(31 ± 4) and (31 ± 5), (29 ± 5) and (29 ± 5) ml/L] decreased significantly compared to the normal control group [(35 ± 4) and (34 ± 4) ml/L, t = 2.18-4.83, all P < 0.05]. The OUES, OUEP and the OUE at the anaerobic threshold in COPD patients were correlated (r = 0.500-0.625, all P < 0.01) positively with the exercise tolerance (peak VO2% pred). CONCLUSIONS: The oxygen uptake efficiency of patients with COPD is significantly reduced compared to that of the normal subjects, and is correlated positively with the exercise capacity.