A double-blind placebo controlled study

• To compare the effect of tadalafil and dexamethasone versus placebo on Ppa and pulmonary edema formation in subjects susceptible to HAPE.
• To investigate the effect of dexamethasone on alveolar fluid clearance, as assessed by measurement of the nasal potential difference, and prevention of HAPE.
• To investigate the effect of the tadalafil and dexamethasone versus placebo on the dynamic CBF autoregulation properties and on the development of AMS in HAPE susceptible subjects.

Inclusion Criteria:

• At least one previous episode of high altitude pulmonary edema

Exclusion Criteria:

• pulmonary arterial hypertension
• congenital heart disease
• any chronic lung disease