Objective        To evaluate the efficacy and safety of oral administration of sildenafil on the treatment of suspected early high altitude pulmonary hypertension (HAPH).        Methods       After a cohort of young males living above 4 500 m screened by medical examination

24 subjects were diagnosed as suspected early HAPH

and enrolled in this study. These subjects were randomly divided into 2 groups

Group A (n=11) who receiving supplemental oxygen

and Group B (n=13) who were treated with oxygen supplement combined with oral taking of 50 mg sildenafil per day for 12 weeks. The subjects were followed-up by telephone. At the end of treatment

6-minute walk test (6MWT)

Borg dyspnea scores

systolic pulmonary arterial pressure (SPAP)

percutaneous oxygen saturation

blood pressure

liver function and kidney function were used to evaluate the efficiency.        Results        After 12 weeks’ intervention

6MWT in group A was improved from (407.53±50.14) m to (444.53±56.36) m (P0.05)

and that in group B was improved from (405.54±42.40) m to (463.34±40.12) m (P0.05)

with the later was obviously improved more than the former (P0.05). Borg dyspnea scores of 2 groups were also obviously improved than before treatment (P0.05)

and still that in group B was obviously improved greater than that in group A (P0.05). SPAP in group A was decreased from (26.25±1.25) mmHg to (25.27±1.10) mmHg (P0.05)

and that in group B decreased from (25.56±1.85) mmHg in the baseline to (21.69±1.88) mmHg (P0.05). Group B was obviously decreased more than group A(P0.05). There was no obvious side effect and change in blood pressure

liver function and kidney function in sildenafil treatment.       Conclusion        Oral administration of sildenafil is an efficient and safe intervention for suspected early HAPH.