Sildenafil and Bosentan Improve Arterial Oxygenation During Acute Hypoxic Exercise: A Controlled Laboratory Trial

Objectives Sildenafil and, recently, bosentan have been reported to increase arterial saturation and exercise capacity at altitude. The mechanisms behind this are still poorly defined but may be related to attenuation of hypoxic pulmonary vasoconstriction (HPV) and improved gas exchange. This study was designed to examine and compare the effect of sildenafil and bosentan on pulmonary gas exchange during acute hypoxic exercise in a controlled laboratory setting. Methods Sixteen athletic university students (8 males, 8 females) were examined during exercise in a hypoxic chamber (11% oxygen) before and after the administration of either sildenafil (n=10) or bosentan (n=6). Respiratory and metabolic measurements were taken at rest and during increasing exercise intensity (up to 90% of their individual maximal oxygen uptake [V̇O2 max]) in concert with arterial blood gas sampling. Results Both drugs resulted in small, but significant increases in arterial PO2 (2–3 Torr) and O2 saturation (3–4%) at rest and during hypoxic exercise, in both men and women. No significant changes in arterial PCO2 or ventilation were seen at rest or during exercise in hypoxia; however, heart rate (both at rest and during exercise) was increased with both sildenafil and bosentan in both men and women. Conclusions These data demonstrate that sildenafil and bosentan equally improve arterial oxygenation in acute hypoxia in both men and women, which could account for improved physical performance at altitude.