Long-term Oxygen Therapy in Patients With Chronic Obstructive Pulmonary Disease Who Live at High Altitude

The subjects will be randomly assigned to receive or not LTOT and they will be followed for 30 months. At baseline and then at 10, 20 and 30 months, they will be clinically evaluated with arterial blood gases, pulse oximetry, echocardiography, spirometry with bronchodilator, diffusion capacity, quality of life (SGRQ), neurocognitive performance (MMSE) and six minutes walk test. The primary outcome will evaluate the ratio of occurrence of erythrocytosis or pulmonary hypertension. Secondary outcomes will be evaluated quality of life, lung function, neurocognitive performance and exercise tolerance by comparing the groups with and without LTOT.