Randomised, placebo controlled study of the effect of sildenafil on hypoxia-induced pulmonary hypertension

INTERVENTION: 1. Placebo tds for 3 months 2. Sildenafil 25 mg tds for 3 months, or 3. Sildenafil 100 mg tds for 3 months CONDITION: Hypoxia‐induced pulmonary hypertension ; Circulatory System ; Hypertension PRIMARY OUTCOME: Not provided at time of registration SECONDARY OUTCOME: Not provided at time of registration INCLUSION CRITERIA: 1. Males or females aged 18 years and over 2. Resting pulmonary artery pressure =25 mmHg 3. Written informed consent must be obtained by the investigator before the subject is screened for the study