RESUMO
BACKGROUND: Individuals with chronic mountain sickness (CMS) show severe hypoxemia, excessive polycythemia, and marked pulmonary hypertension. The pathophysiologic mechanisms of CMS are still not completely understood. METHODS: We determined plasma atrial natriuretic peptide (ANP), red cell 2,3-diphosphoglycerate (2,3-DPG), hematocrit, hemoglobin, and arterialized ear lobe blood gas values in 13 patients with CMS (9 Hans, 4 Tibetans) and 18 control Han Chinese men of similar age, height, and weight who had been living at 4300 m on the Tibetan plateau of Qinghai Province, China, for approximately 14 years. RESULTS: A significantly higher level of ANP was found in the CMS patients compared to the non-CMS patients (113.4+/-5.5 pg/mL vs 87.6+/-4.7 pg/mL, P < .01), and the levels of ANP correlated positively with the hemoglobin concentration (r = 0.8282, P < .01). The 2,3-DPG levels in the CMS patients were significantly increased compared to the non-CMS subjects (5.23+/-0.16 mmol/L vs 4.40+/-0.12 mmol/L, P < .01), and the 2,3-DPG concentrations in the CMS patients were negatively correlated with their PaO2 values (r = -0.7898, P < .01). The CMS patients had significantly higher PaCO2 levels, lower pH values, lower PaO2 levels, and greater alveolar-arterial oxygen differences (PAO2 - PaO2) compared to the non-CMS subjects. CONCLUSIONS: These findings suggest that overproduction of ANP and 2,3-DPG at high altitudes may play an important role in the pathophysiology of chronic mountain sickness.