Oxygen transport versus hemoglobin.
Curve adapted from references 1 –3.
Oxygen transport increases with increasing hemoglobin until viscosity effects reduce flow and transport. The point at which oxygen transport is maximum is indicated as Hbmax. In erythrocytoses such as secondary polycythemias, there is both increased red cell volume and increased total blood volume. Increased cardiac output allows the curve to move up and to the right, dramatically increasing oxygen transport along with the Hbmax. In sickle cell anemia, the decreased hemoglobin and higher blood viscosity due to the presence of sickle cells shift the curve sharply to the left, decreasing the Hbmax. Oxygen transport can remain at normal rather than decreased levels due to increased cardiac output.
