PeakP_ETCO₂ combined with FEV1/FVC predicts vasodilator-responsive patients with idiopathic pulmonary arterial...

Cardiopulmonary exercise testing and pulmonary function test are important methods for detecting human cardio-pulmonary function. Whether they could screen vasoresponsiveness in idiopathic pulmonary artery hypertension (IPAH) patients remains undefined. One hundred thirty-two IPAH patients with complete data were retrospectively enrolled. Patients were classified as vasodilator-responsive (VR) group and vasodilator-nonresponsive (VNR) group on the basis of the acute vasodilator test. Pulmonary function test and cardiopulmonary exercise testing were assessed subsequently and all patients were confirmed by right heart catheterization. We analyzed cardiopulmonary exercise testing and pulmonary function test data and derived a prediction rule to screen vasodilator-responsive patients in IPAH. Nineteen of VR-IPAH and 113 of VNR-IPAH patients were retrospectively enrolled. Compared with VNR-IPAH patients, VR-IPAH patients had less severe hemodynamic effects (lower RAP, m PAP, PAWP, and PVR). And VR-IPAH patients had higher anaerobic threshold (AT), peak partial pressure of end-tidal carbon dioxide (P_ETCO₂), oxygen uptake efficiency (OUEP), and FEV₁/FVC (P all <0.05), while lower peak partial pressure of end-tidal oxygen (P_ETO₂) and minute ventilation (VE)/carbon dioxide output (VCO₂) slope (P all <0.05). FEV₁/FVC (Odds Ratio [OR]: 1.14, 95% confidence interval [CI]: 1.02-1.26, P = 0.02) and PeakP_ETCO₂ (OR: 1.13, 95% CI: 1.01-1.26, P = 0.04) were independent predictors of VR adjusted for age, sex, and body mass index. A novel formula (=-16.17 + 0.123 × PeakP_ETCO₂ + 0.127×FEV₁/FVC) reached a high area under the curve value of 0.8 (P = 0.003). Combined with these parameters, the optimal cutoff value of this model for detection of VR is -1.06, with a specificity of 91% and sensitivity of 67%. Compared with VNR-IPAH patients, VR-IPAH patients had less severe hemodynamic effects. Higher FEV₁/FVC and higher peak P_ETCO₂ were associated with increased odds for vasoresponsiveness. A novel score combining PeakP_ETCO₂ and FEV₁/FVC provides high specificity to predict VR patients among IPAH.