During ascent to high altitude there is a physiologic response to hypoxia that results in an
elevated pulmonary arterial pressure associated with decreased exercise performance,
altitude-induced pulmonary hypertension, and high altitude pulmonary edema (HAPE). Riociguat
is a novel agent from Bayer Pharmaceuticals that has already demonstrated effectiveness in
the treatment of pulmonary hypertension, and it may prove to be beneficial in cases of
altitude-induced pulmonary hypertension or HAPE. This research study, composed of 20 healthy
volunteers ages 18-40 years, will attempt to mimic the decreased oxygen supply and elevated
pulmonary artery pressures found in conditions of high altitude, allowing observation of the
effects of riociguat and exercise on pulmonary arterial pressure, arterial oxygenation, and
exercise performance. Prior to entering the hypobaric chamber, subjects will have radial
arterial lines and pulmonary artery catheters placed to obtain arterial and pulmonary artery
pressure measurements. Subjects will then enter the hypobaric chamber and perform exercise
tolerance tests at a simulated altitude of 15,000 feet on an electrically braked ergometer
(exercise bike) before and after administration of riociguat. If, after administration of
riociguat and exposure to a simulated altitude of 15,000 feet, the exercise performance is
improved and observed pulmonary artery pressures are lower than those measurements seen prior
to administration of riociguat, this could lead to development of a prophylactic and/or
treatment strategy for HAPE and high-altitude pulmonary hypertension. Statistical analysis
will compare the variables of pulmonary artery pressure, radial arterial pressure,
ventilation rate, cardiac output, PaO2, and work rate at exhaustion before and after
administration of the drug riociguat. The investigator’s hypothesis is that riociguat will
decrease pulmonary artery pressure and improve gas exchange and exercise performance at
altitude.