High-Altitude Polycythemia Study

This study aims to evaluate the clinical efficacy of non-invasive ventilation (NIV) in treating patients with high-altitude polycythemia (HAPC). Participants will be enrolled according to the international diagnostic criteria for high-altitude polycythemia. The study will use both retrospective cohort and prospective study methods. All participants will receive standard basic care. In addition, the intervention group will receive non-invasive ventilation treatment using either BiPAP or CPAP mode. Key measurements, including routine blood tests, liver function, renal function, uric acid, blood lipid profile, electrocardiogram and echocardiography, will be collected as primary and secondary outcome measures to assess the effects of the treatment.