Oxygen Uptake Efficiency Evaluation On Cardiopulmonary Function In Pulmonary Arterial Hypertension

[Objective] To investigate the differences in oxygen uptake efficiency between IPAH and CTEPH, and to assess the relationship between cardiopulmonery function with exercise endurance and the severity of the disease.[Methods] Right heart catheterization, six-minute walk test, routine pulmonary function test and cardiopulmonary exercise testing were underwent in 44 patients with IPAH and 29 patients with CTEPH.[Results] Compared with CTEPH patients, IPAH patients had higher Oxygen uptake efficiency plateau(OUEP), oxygen uptake efficiency at AT(OUE@AT) and lower ·VE/·VCO2 slope, Lowest·VE/·VCO2 [(26.6±5.1)vs(22.7±4.9)ml/L;(25.3 ± 4.7)vs(21.6±5.1)ml/L; 51.4±15.5)vs(66.3±20.0)L/min/L/min;(46.3±9.1) vs(55.6±10.8) L/min/L/min, all p < 0.05, respectively]. Pearson correlation analysis showed, OUEP had a correlation with HR_AT(r=0.376, p < 0.05) but no statistical significant correlation was found with ·VE_AT(r=-0.074, p > 0.05) in patients with IPAH, that was contrary to patients with CTEPH. In both subgroups, OUEP showed a positive correlation with oxygen pulse_AT and peak ·VO2(r = 0.428 ~ 0.723,all p<0.05). And OUEP, peak oxygen uptake were higher in patients in WHO functional class I/II than those in WHO class III/IV(all p ≤ 0.05).[Conclusions] Our study shows that oxygen uptake efficiency and ventilatory efficiency are significantly higher in IPAH than in CTEPH, probably due to differences in heart rate and ventilation. OUEP could appropriately evaluate exercise capacity and the severity of PH.