Sildenafil for Enhanced Performance at High Altitude?

For centuries, reduced exercise tolerance at high altitudeshas frustrated mountaineers and has puzzled scientists. Horace-Benedict de Saussure, who led the second ascent to Mont Blanc (altitude, 4807 m) in 1787, recorded his pulse, respirations, temperature, and symptoms and wrote: The sort of weariness which proceeds from the rarity of the air is absolutely insurmountable; when it is at its height, the most imminent peril will not make you move a step faster.... Since the air had hardly more than half of its usual density, compensation had to be made for the lack of density by the frequency of respi-rations. That is the cause of the fatigue that one expe-riences at great heights. For while the respiration is accelerating, so is the circulation (1). Although de Saussure correctly attributed the de-creased exercise capacity at altitude to the cardiorespirator