OBJECTIVETo explore the effect of prophylaxis on youth's chronic mountain sickness(CMS) who moved to an altitude of above 5 000 meters by long-term oxygen therapy (LTOT).

METHODSNinety-six male youth stationed at 5 070 m, 5 200 m and 5 380 m took oxygen continuously by nasal cannula (LTOT group) every body per day. One year later, epidemiological survey were carried out according to the international CMS diagnostic criteria consist of examining right ventricle end-diastolic dimension (RVED), right ventricular anterior wall (RVAW), right ventricular outflow tract (RVOT), main pulmonary artery (MPA), left ventricular end systolic diameter (LVSD) by ultrasonic diagnostic apparatus, and blood test of alanine aminotransferase (ALT), aspartate aminotransferase (AST), gamma-glutamyl transpeptidase (gamma-GT), creatine kinase (CK), lactate dehydrogenase (LDH), superoxide dismutase (SOD), malondialdehyde (MDA), nitric oxide (NO), nitric-oxide synthase (NOS) blood oxygen saturation (SaQ2). Then, they were compared with 91 males in the same group stationed at the same altitude (without any interventions, control group).

RESULTS(1) The epidemiological survey showed that, SaO2 were increased significantly (P < 0.05) and the prevalence rate of CMS were decreased compared with that of control group (P < 0.05). (2) Echocardiography showed that SOD, NO, NOS were increased (P < 0.05 or 0.01) and LVSD, MPA had no significant difference compared with that of control group (P > 0.05). (3) Biochemical index showed that, SOD, NO, NOS were increased (P < 0.05 or 0.01), MDA, ALT, AST, LDH were decreased (P < 0.05 or 0.01) and gamma-GT, CK had no significant difference compared with that of the control group.

CONCLUSIONAt high altitude, LTOT can reduce lipid peroxidation, improve the important organ injuries caused by hypoxia and protect the mitochondria respiratory function and play an important role on the prevention of chronic mountain sickness.