Background and objective: Clinical presentations associated with chronic thromboembolic pulmonary hypertension (CTEPH) and pulmonary arterial hypertension (PAH) at rest are highly similar. Differentiating between CTEPH and PAH using non-invasive techniques remains challenging. Thus, we examined whether analysis of ventilatory gas in response to postural changes can be useful as a non-invasive screening method for pulmonary hypertension (PH), and help differentiate CTEPH from PAH. Methods: We prospectively enrolled 90 patients with suspected PH and performed right heart catheterization, ventilation/perfusion scan and ventilatory gas analysis. Various pulmonary function parameters were examined in the supine and sitting postures, and postural changes were calculated (Δ(supine − sitting)). Results: In total, 25 patients with newly diagnosed PAH, 40 patients with newly diagnosed CTEPH and 25 non-PH patients were included. ΔEnd-tidal CO2 pressure (PETCO2) was significantly lower in patients with CTEPH and PAH than in non-PH patients (both P < 0.001). ΔPETCO2 < 0 mm Hg could effectively differentiate PH from non-PH (area under the curve (AUC) = 0.969, sensitivity = 89%, specificity = 100%). Postural change from sitting to supine significantly increased the ratio of ventilation to CO2 production (VE/VCO2) in the CTEPH group (P < 0.001). By contrast, VE/VCO2 significantly decreased in the PAH group (P = 0.001). Notably, CTEPH presented with higher ΔVE/VCO2 than PAH, although no differences were observed in haemodynamic and echocardiographic parameters between the two groups (P < 0.001). Furthermore, ΔVE/VCO2 > 0.8 could effectively differentiate CTEPH from PAH (AUC = 0.849, sensitivity = 78%, specificity = 88%). Conclusion: Postural changes in ventilatory gas analysis are useful as a non-invasive bedside evaluation to screen for the presence of PH and distinguish between CTEPH and PAH.
- cardiovascular diseases
- pulmonary circulation, pulmonary hypertension
- pulmonary gas exchange
- pulmonary ventilation