Exercise hyperventilation and pulmonary gas exchange in chronic thromboembolic pulmonary hypertension: Effects of balloon pulmonary angioplasty

BACKGROUND: Excessive ventilation ((V)over dotE) and abnormal gas exchange during exercise are features of chronic thromboembolic pulmonary hypertension (CTEPH). In selected CTEPH patients, balloon pulmonary angioplasty (BPA) improves symptoms and exercise capacity. How BPA affects exercise hyperventilation and gas exchange is poorly understood. METHODS: In this longitudinal observational study, symptom-limited cardiopulmonary exercise tests and carbon monoxide lung diffusion (DLCO) were performed before and after BPA (interval, mean (SD): 3.1 (2.4) months) in 36 CTEPH patients without significant cardiac and/or pulmonary comorbidities. RESULTS: Peak work rate improved by 20% after BPA whilst (V)over dotE at peak did not change despite improved ventilatory efficiency (lower (V)over dotE with respect to CO2 output [(V)over dotCO(2)]). At the highest identical work rate pre-and post-BPA (75 (30) watts), (V)over dotCO(2)E and alveolar-arterial oxygen gradient (P(Ai-a)O-2) decreased by 17% and 19% after BPA, respectively. The physiological dead space fraction of tidal volume (VD/VT), calculated from measurements of arterial and mixed expired CO2, decreased by 20%. In the meantime, DLCO did not change. The best correlates of P(Ai-a) O2 measured at peak exercise were physiological VD/VT before BPA and DLCO after BPA. CONCLUSIONS: Ventilatory efficiency, physiological VD/VT, and pulmonary gas exchange improved after BPA. The fact that DLCO did not change suggests that the pulmonary capillary blood volume and probably the true alveolar dead space were unaffected by BPA. The correlation between DLCO measured before BPA and P(Ai-a)O2 measured after BPA suggests that DLCO may provide an easily accessible marker to predict the response to BPA in terms of pulmonary gas exchange. (C) 2021 International Society for Heart and Lung Transplantation. All rights reserved.