Hemoglobin oxygen dissociation (P50) in bronchopulmonary dysplasia

A study was devised to determine the P50 in infants with bronchopulmonary dysplasia (BPD). Other factors such as red blood cell 2,3-diphosphoglycerate (2,3-DPG) level proportions of adult (HbA) to fetal (HbF) hemoglobins which could affect P50 were also measured. Fourteen infants with clinical and radiological signs of BPD with a mean post-conceptional age of 42.2 +/- 4.7 weeks born at a mean gestational age of 29.3 +/- 2.0 weeks were evaluated. The percentage of HbF determined in 8 infants was 40.1 +/- 20.3% and the mean 2,3-DPG concentrations was 13.1 +/- 2.2 mumol/g Hb. The P50 was 25.1 +/- 2.7 mm Hg (range 18-29.5 mm Hg). When a HbO2 curve was established based on a large volume of blood consisting of adult blood and newborn cord blood mixed to attain a P50 of 25.1 mm Hg, the PaO2 at 90% O2 saturation was 52 mm Hg. Since there can be a wide range in HbO2 in infants with chronic BPD, pulse oximetry remains the most prudent method of monitoring oxygen therapy in BPD infants.