Hemoglobin-oxygen equilibrium in cystic fibrosis.

A study of 35 patients with cystic fibrosis demonstrated that increasing severity of pulmonary involvement was associated with a mild but definite increase in erythrocyte 2,3-diphosphoglycerate (2,3-DPG) and a decrease in hemoglobin affinity for oxygen. The predominant regulators of 2,3-DPG were blood pH, cardiac output, and systemic oxygen transport. No significant relationship was observed between erythrocyte 2,3-DPG content and arterial oxygen tension. Hypophosphatemia may have prevented a greater increase in erythrocyte 2,3-DPG content. The inadequate increase in 2,3-DPG and consequent insufficient change in hemoglobin-oxygen affinity, coupled with an insufficient compensatory erythrocytic response, may adversely affect tissue oxygenation in patients with severe cystic fibrosis.