This study examined the influence of oral sildenafil on pulmonary haemodynamics and exercise tolerance during hypoxia induced pulmonary hypertension in healthy mountaineers and trekkers who were not susceptible to high altitude pulmonary oedema. Fourteen healthy volunteers (12 men, median age 36.5 years) were enrolled and randomised in a double blind, placebo controlled, crossover design. Participants were assigned to receive placebo or one 50 mg dose of sildenafil. Systolic pulmonary artery pressure, cardiac output, and peripheral arterial oxygen saturation at rest and during assessment of maximum exercise capacity on cycle ergometry were measured, both while breathing a hypoxic gas mixture with 10% fraction of inspired oxygen at low altitude and then at the Mount Everest base camp (5400 m).

Sildenafil reduced hypoxic pulmonary hypertension at rest and with exercise, and increased maximum exercise capacity and cardiac output. The study did not examine the effects of sildenafil on normoxic exercise tolerance, and the authors cautioned about the unclear role of sildenafil in the management of acute mountain sickness. In addition, it is not known whether sildenafil increases exercise capacity in hypoxic pulmonary hypertension due to lung diseases such as COPD.