Interest in the erythropoietic response in patients with chronic lung disease stems from the fact that, despite arterial hypoxia, the hemoglobin concentration is usually normal.1-6 Hypoxia under almost all other conditions is associated with a secondary polycythemia. In natives of the Peruvian Andes, Hurtado and co-workers clearly demonstrated that prolonged exposure to high altitudes will produce an increase in hemoglobin and hematocrit proportional to the degree of hypoxia.7 Similarly, it has been observed that patients with arterial hypoxemia due to cyanotic heart disease8,9 and occasionally due to chronic pulmonary disease have secondary polycythemia.
The apparent lack of erythropoietic response in most patients with chronic pulmonary disease has not been explained adequately. Recently it has been emphasized that, if total red cell volume is measured rather than peripheral hemoglobin and hematocrit, patients with chronic pulmonary disease will demonstrate an adequate erythropoietic response.10 However, the reported data