Abstract: Objective To investigate the efficacy of oxygen uptake efficiency slope (OUES) on evaluation the cardiopulmonary function of patients with chronic obstructive pulmonary disease (COPD). Methods The cardiopulmonary function of 54 stable COPD patients with the cardiopulmonary function of Ⅱ~Ⅳ were evaluated, following a symptom-limited Steep protocol with simultaneous respiratory gas measurement,they were performed exercise tests on a treadmill, simultaneously the oxygen uptake (VO2), carbon dioxide production (VCO2),peak oxygen uptake (VO2peak), minute ventilation (VE), and respiratory gas exchange rate (RER) were measured. OUES was derived from the relation between VO2 and VE during incremental exercise and was determined by VO2=algVE+b, where a=OUES, to measure anaerobic threshold (VAT) meanwhile. Results OUES correlated with the VO2peak (P<0.001). 75% OUES, 90% OUES and 100% OUES were not significantly different (F=0.239, P=0.830). Conclusion OUES can respond the cardiopulmonary function in patients with COPD, 75% OUES from sub-maximal exercise can be an index for cardiopulmonary function.

Key words: chronic obstructive pulmonary disease, oxygen uptake efficiency slope, pulmonary rehabilitation, cardiopulmonary function