Analysis of Oxygenation in Chronic Thromboembolic Pulmonary Hypertension Using Dead Space Ratio and Intrapulmonary Shunt Ratio.

Current therapeutic methods for chronic thromboembolic pulmonary hypertension (CTEPH) can improve hemodynamic status and are expected to improve prognoses. However, some patients experience dyspnea during effort and continue supplemental oxygenation despite their hemodynamic status being fully improved. Considering the pathogenesis of CTEPH, the dead space and intrapulmonary shunt are assumed to be responsible for hypoxia in CTEPH, but their contributions are unclear. It is also unclear whether they are improved after treatment. The aim of this study was to investigate the implications of the dead space ratio (DSR) and the intrapulmonary shunt ratio (ISR) for hypoxia in CTEPH and treatment for CTEPH.We retrospectively measured the DSR and ISR of 23 consecutive patients with CTEPH. For 11 of these 23 (10 were treated by balloon pulmonary angioplasty, one with riociguat), we also measured these parameters before and after CTEPH treatments. Overall, the DSR and ISR were abnormally elevated (DSR: 0.63 ± 0.06; ISR: 0.20 ± 0.05). After treatment, mean pulmonary artery pressure was improved (from 40.3 ± 8.1 to 25.5 ± 2.7 mmHg). Although atrial oxygen saturation (SaO2), DSR and ISR were improved (SaO2: from 90.2 ± 3.2 to 93.7 ± 1.8%; DSR: from 0.64 ± 0.06 to 0.58 ± 0.05; ISR: from 0.20 ± 0.04 to 0.18 ± 0.02), these improvements were slight compared with that of mean pulmonary artery pressure.The DSR and ISR were abnormally elevated in patients with CTEPH and their improvement by treatment was limited. Only DSR can be a useful marker for normalization of hypoxia in CTEPH.