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

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