Developmental Changes in the Oxygen Equilibrium Curve of Infants as Related to the |[lsquo]|Functioning DPG Fraction|[rsquo]| and Its Alteration with Disease

摘要

The red cell organic phosphate 2, 3-diphosphoglycerate (DPG) has been shown to bind to adult hemoglobin and decrease its affinity for oxygen while it has little effect on altering the oxygen equilibrium curve of fetal hemoglobin. Sequential studies of the P50 (partial pressure of oxygen at which hemoglobin is 50% saturated), fetal hemoglobin and red cell DPG were performed in 31 term and 28 premature infants. In term infants the P50 averaged 19.4 mm Hg on day 1; 20.6 on day 5; 26.6 at 3–4 months amd 28.0 at 6 months (normal adults 27.5=0.8). The initial P50 of the premature infants was lower and its change with age more gradual. The P50 did not correlate precisely with the percent fetal hemoglobin alone or the DPG alone but correlated significantly with the product of the percent adult hemoglobin times the DPG content (‘functioning DPG fraction’). Calculations indicate that the term infants at age 3 months with a hemoglobin of 11.0 g% is delivering more oxygen to his tissues at a mean venous PO2 of 40 mm Hg than is the newborn with a hemoglobin of 17.0 g%. sick infants were found to have low P50's and DPG levels. Infants given either simple or exchange transfusions of fresh adult blood showed an increased ‘functioning DPG fraction’, a shift of the oxygen equilibrium curve to the right and their oxygen unloading capacity reached that of a 6-month infant. Such treatment appears useful in the sick infant because it facilitates peripheral oxygen delivery to the tissues.