The effect of high altitude (2500 m) on incremental cycling exercise in patients with pulmonary arterial hypertension and chronic thromboembolic pulmonary hypertension: a randomised controlled cross-over trial
Julian Müller, Anna Titz, Simon Schneider, Meret Bauer, Laura Mayer, Lea Lüönd, Tanja Ulrich, Michaël Furian, Aglaia Forrer, Esther I. Schwarz, Konrad E. Bloch, Mona Lichtblau, Silvia Ulrich
Abstract
Objective To investigate the effect of a daylong exposure to high altitude on peak exercise capacity and safety in stable patients with pulmonary arterial and chronic thromboembolic pulmonary hypertension (PAH/CTEPH). Methods In a randomised controlled cross-over trial, stable patients with PAH or distal CTEPH without resting hypoxemia at low altitude performed two incremental exercise tests to exhaustion, one after 3–5 h at high (2500 m) and one at low altitude (470 m). Results In 27 patients with PAH/CTEPH (44% women, 61±14 y), maximal work-rate was 110±64 watts at 2500 m and 123±64 watts at 470 m (−11%, 95%CI: −16 to −11, p<0.001). SpO 2 and PaO 2 at end-exercise were 83±6% versus 91±6% and 6.1±1.9 kPa versus 8.6±1.9 kPa (−8%; −29%; both p<0.001) at 2500 m versus 470 m, respectively. Maximal oxygen uptake at high altitude was 17.8±7.5 L·min −1 ·kg −1 versus 20±7.4 L·min −1 ·kg −1 at low altitude (−11%, p<0.001). At end-exercise, the ventilatory equivalent for CO 2 was 43±9 at 2500 m versus 39±9 at 470 m (+9%, 95%CI: 2 to 6; p=0.002). No adverse events occurred during or after exercise. Conclusion Among predominantly low-risk patients with stable PAH/CTEPH, cycling exercise during the first day at 2500 m was well tolerated, but peak exercise capacity, blood oxygenation and ventilatory efficiency were lower compared to 470 m.