Cardiopulmonary Exercise Testing To Evaluate Ventilation Efficiency In Patients With Pulmonary Arterial Hypertension

[Objectives]:To investigate the differences in ventilation efficiency in patients with IPAH and CTEPH, and to evaluate the correlations of ventilatory efficiency with exercise capacity and the severity of the diseases.[Methods]:We performed cardiopulmonary exercise testing in 66IPAH and 44CTEPH patients.[Results]:The ventilatory equivalent for CO2 at anaerobic threshold (EqO2_AT) was significantly higher in CTEPH than those in IPAH (55.97 L/min/L/min vs 46.82 L/min/L/min, p<0.05). In addition, The V E/VCO2 slope and Lowest VE/V CO2 were higher in patients with CTEPH than patients with IPAH (50.04L/min/L/min vs 60.64 L/min/L/min, p<0.05; 44.51 L/min/L/min vs 53.62 L/min/L/min, p<0.05). Correspondingly, Peak oxygen uptake(Peak V O2/kg) was markedly higher in IPAH versus CTEPH (14.9mL/kg/min vs 13.3 mL/kg/min, p<0.05). Peak V O2 correlated significantly with EqO2_AT, V E/V CO2 slope and Lowest V E/V CO2 in both IPAH and CTEPH groups; But correlation coefficients were higher in the IPAH than the CTEPH group. A multivariate linear regression analysis found that disease subtype was a independent predictor of EqO2_AT, VE/VCO2 slope, Lowest VE/VCO2. Furthermore, the EqO2_AT, VE/VCO2 slope, Lowest VE/VCO2 could differentiate between world health organization function classes Ⅰ/Ⅱ and Ⅲ/Ⅳ in IPAH but not CTEPH.[Conclusions]:The present study shows that ventilatory inefficiency is greater likely due to increased heterogeneous pulmonary perfusion which may attribute to pulmonary vascular obliteration in CTEPH in spite of the fact that pulmonary hemodynamic impairment is more mild in CTEPH than IPAH.