Polycythemia in chronic obstructive pulmonary disease. A study of serum and urine erythropoietin and medullary erythroid progenitors.

In order to investigate the mechanism of polycythemia in chronic obstructive pulmonary disease (COPD), serum and urinary levels of erythropoietin and medullary erythroid progenitors were studied in 21 patients; nine were nonpolycythemic (hematocrit, 39 +/- 4 percent; red blood cell [RBC] mass, 28 +/- 5 ml/kg; forced expiratory volume in one second [FEV1], 0.6 +/- 0.1 L), and 12 patients were polycythemic (hematocrit, 52 +/- 7 percent; RBC mass, 46 +/- 7 ml/kg; FEV1, 0.9 +/- 0.3 L). Hypoxia was severe in both groups, with mean arterial oxygen pressure of 47 mm Hg. The following parameters of tissue oxygenation were not significantly different between the two groups: arterial and mixed-venous oxygen saturations; cardiac output; oxygen utilization coefficient; 2, 3-diphosphoglycerate, and carboxyhemoglobin level. The level of erythropoietin was measured by bioassay in vitro. The level was increased in the serum of 85 percent (18) and in the urine of 38 percent (8) of the patients. There was no significant difference between the nonpolycythemic and polycythemic groups. Without exogenous erythropoietin, none of the subjects showed spontaneous colonies of erythroid progenitors. The addition of one unit of erythropoietin induced a similar normal proliferation of erythroid progenitors in both groups. The absence of adaptative polycythemia in the nonpolycythemic group with severe hypoxia was seemingly related neither to a quantitative deficit of erythropoietin nor to a lack of sensitivity of erythroid progenitors to its action.