RT Journal Article SR Electronic T1 Clinical usefulness of end-tidal CO2 profiles during rapidly-incremental exercise in patients with idiopathic and chronic thromboembolic pulmonary hypertension JF European Respiratory Journal JO Eur Respir J FD European Respiratory Society SP P3974 VO 42 IS Suppl 57 A1 Roberta Ramos A1 Eloara Ferreira A1 Arakaki-Ota Jaquelina A1 Erika Treptow A1 Luiz Nery A1 J. Alberto Neder YR 2013 UL http://erj.ersjournals.com/content/42/Suppl_57/P3974.abstract AB Rationale: Low CO2 set-point and inequalities in ventilation/perfusion distribution can lead to reduced end-tidal partial pressure for CO2 during incremental exercise in pulmonary arterial hypertension (PAH). Whether progressive or sudden decreases in exercise PETCO2 could be helpful in indicating more severe disease remains unclear. Methods: 43 patients with chronic thromboembolic pulmonary hypertension (CTEPH) (50 ± 13 yrs, mPAP 53 ± 11 mmHg) and 18 with idiopathic PAH (39 ± 14 yrs, mPAP 63 ± 17 mmHg) performed a ramp-incremental exercise test. According to PETCO2, they were separated into: 1) Group A with a normal response; 2) Group B, showing an abrupt decrease and other signs of exercise-induced right-to-left shunt (EIS); and 3) Group C, showing a progressive decrease but without EIS. Results: In CTEPH, Group B (n = 21/43, 48%) had worse haemodynamics (cardiac index= 1.9±0.6 vs 2.3±0.6 L/min/m2), more impaired exercise performance (peak O2 uptake= 12±2 vs 14±2 mL/kg/min) and higher ventilatory response (ΔV'E/VCO2= 70±22 vs 47±8, p<0.05) compared to Group A. Similar findings were observed in IPAH. Of note, Group C pattern was more frequent in CTEPH than in IPAH (28% vs 11%, p<0.05) and associated with functional impairments at rest and exercise at same extent of those found in Group B. Conclusion: Abnormal decrease in PETCO2 during exercise is more commonly found in CTEPH than PAH and regardless its association with right-to-left shunt.should be clinically valued as a non-invasive marker of disease severity in both diseases.