PCO2 and room air saturation values in premature infants at risk for bronchopulmonary dysplasia

Objective:To determine the capillary partial pressure of carbon dioxide (PCO2) and room air transcutaneous hemoglobin saturation (RA SAT) at 36 weeks’ postmenstrual age (PMA) in infants born with weight between 501 and 1250 g.Study Design:Multicenter, prospective investigation with primary data collection within 72 h of 36 weeks PMA or discharge, whichever first. PCO2 and RA SAT determinations were done at rest on infants not requiring mechanical ventilation or nasal continuous positive airway pressure (NCPAP).Result:A total of 220 infants were enrolled (mean gestational age 27.7 weeks, mean birthweight 951 g). In infants with traditionally defined chronic lung disease (CLD) compared to those without CLD, the mean PCO2 was significantly higher (54 versus 45 mm Hg) and the median RA SAT significantly lower (<80 versus 97%). In infants with the new classification of bronchopulmonary dysplasia (BPD), there was a significant linear trend toward increasing PCO2 with increasing severity of BPD (45, 47, 54 and 62 mm Hg in No, Mild, Moderate and Severe BPD). There was a significant linear trend toward decreasing RA SAT with increasing severity of BPD (97, 95 <80, <80% in No, Mild, Moderate and Severe BPD).Conclusion:Defining CLD as BPD based upon a RA SAT test is a more discriminate, objective method to categorize lung injury. PCO2 is an objective measure of lung function that inversely correlates with RA SAT. These determinations done together at 36 weeks PMA may provide more precise and accurate estimates of lung injury that might allow for better understanding of pulmonary therapies and clearer comparison of BPD rates and severities among NICUs.