Objective: To explore the characteristics of oxygen uptake efficiency (OUE) in patients with pulmonary hypertension (PH) and analyze the correlation between OUE and exercise capacity.
Methods: A total of 76 PH patients and 29 healthy controls at Shanghai Pulmonary Hospital between October 2010 and January 2014 were evaluated. All PH patients were classified into 4 groups according to the World Health Organization functional class (WHO-FC). Pulmonary function and cardiopulmonary exercise tests were performed in all subjects.
Results: Compared with health control, the PH patients had lower forced vital capacity (FVC) of expected value (%pre), forced expiratory volume in one second (FEV(1))%pre and FEV(1)/FVC ((81.9 ± 15.5)% vs (88.6 ± 14.1)%, (75.0 ± 16.4)% vs (85.2 ± 17.2)% and (78.3 ± 9.3)% vs (88.3 ± 7.3)%, all P < 0.05). Compared with control group, there were also significant reductions in oxygen uptake efficiency slope (OUES), oxygen uptake efficiency plateau (OUEP) and OUE at the anaerobic threshold ((1.14 ± 0.42) vs (2.32 ± 0.34) (L/min)/lg (L/min), (27 ± 5) vs (37 ± 4) ml/L, (24 ± 6) vs (34 ± 5) ml/L, all P < 0.05). No significant differences existed in OUES, OUEP and OUE at the anaerobic threshold in PH patients between WHO-FC Iand WHO-FC II groups. There were significant differences in OUE among other groups (all P < 0.05). And OUES, OUEP and OUE at the anaerobic threshold were correlated positively with exercise tolerance in PH patients.
Conclusion: OUE significantly declines in PH patients compared with normal subjects and it is correlated positively with exercise capacity.