Non‐invasive screening using ventilatory gas analysis to distinguish between chronic thromboembolic pulmonary hypertension and pulmonary arterial hypertension

Abstract

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.

Drug discovery focused on novel pathogenic proteins for pulmonary arterial hypertension

“…In patients with advanced stage, the prognosis is poor even with the use of pulmonary vasodilators, and thus, the development of essential therapeutic agents is awaited [ 3 , 4 ]. We have been conducting basic and clinical research on pulmonary hypertension for many years [5][6][7][8][9][10][11][12][13][14][15]. To date, we have discovered novel pathogenic proteins involved in pulmonary hypertension and are proceeding with drug discovery and biomarker development [16][17][18][19].…”

Postural changes from ventilatory gas exchange in pulmonary hypertension: Is it a practical solution to a complex question?

“…3 In a recent publication in Respirology, Akizuki et al assess an interesting question: whether postural changes during resting ventilatory gas analysis may be used as a non-invasive tool to screen for PH and to differentiate PAH from CTEPH. 8 Changes in body position were assessed in the supine and sitting positions (Δ supine − sitting), and compared postural changes in minute ventilation (⩒e), tidal volume (VT), respiratory rate, oxygen uptake (⩒O 2 ), carbon dioxide output (⩒CO 2 ) and end-tidal carbon dioxide (P ET CO 2 ) in subjects with PAH (n = 25), CTEPH (n = 40) and controls without PH (n = 25).…”