[Secondary polycythemia and gasometric changes in chronic bronchopneumopathies with respiratory insufficiency]

42 patients with chronic bronchopneumopathy were divided into 2 groups: one with polyemia (15 patients) and the other without polyemia (27 patients). There was no statistical significant differences in median age, clinical evolution nor basal medium arterial PO2 value (43 +/- 12 and 48 +/- 11 mm Hg); while there was an increase of median basal PCO2 in patients with polyemia (54 +/- 8.4 and 48 +/- 9.3; P < 0.025). There was direct correlation between PCO2 and Hb levels in the whole series (r = 0.42; P < 0.01) and equal correlation in the limit of statistical signification between PCO2 and red cells (r = 0.29; P = 0.05). The correlation between these hematic values and the PO2 values of the whole series was not significant, this taking into account the logical inverse relation between them, because of the important role of hypoxia in developing polyemia. The correlation between PO2 and PCO2 was inverse and significant (r = -0.33; P < 0.05). These findings show the apparent influence of CO2 retention to produce polyemia, apart from the effects of hypoxia, being the opposite of the results in experimental studies which showed a stoppage of the erythropoietin production by CO2 effects. The probable explanation is that patients with more PCO2 had more intense respiratory malfunction than lower PCO2 patients, producing night episodes of more basal hypoxia, this being a major stimulus of polyemia.