Significance of Hypocapnia in the Risk Assessment of Patients with Pulmonary Hypertension

Blood gas analysis is part of the diagnostic work−up for pulmonary hypertension (PH). Although some studies have found that the partial pressure of carbon dioxide (PaCO(2)) is an independent marker of mortality in individuals with pulmonary arterial hypertension (PH Group 1), there is a lack of data regarding the significance of PaCO(2) in individuals with different types of PH based on the new 2022 definitions. Therefore, this study analyzed data from 157 individuals who were undergoing PH work−up, including right heart catheterization, using PH definitions from the 2022 European Society of Cardiology/European Respiratory Society guidelines. At diagnosis, N−terminal pro−B−type natriuretic peptide (NT−pro−BNP) levels were significantly higher, but the time−course of NT−pro−BNP levels during treatment was significantly more favorable in individuals with pulmonary arterial hypertension (PH Group 1) who did versus did not have hypocapnia (p = 0.026 and p = 0.017, respectively). These differences based on the presence of hypocapnia were not seen in individuals with PH Groups 2, 3, or 4. In conclusion, using the new definition of PH, hypocapnia may correlate with worse risk stratification at diagnosis in individuals with pulmonary arterial hypertension. However, hypocapnic individuals with pulmonary arterial hypertension may benefit more from disease−specific therapy than those without hypocapnia.