ENDOGENOUS FORMATION OF CARBON MONOXIDE IN NEWBORN INFANTS:IV. On the Relation between the Blood Carboxyhaemoglobin Concentration and the Pulmonary Elimination of Carbon Monoxide

Summary A procedure for the determination of the pulmonary elimination of carbon monoxide in newborn infants has been described. Quantitative collection of the expired air was accomplished with the aid of an open circuit breathing system. The low CO concentrations in room air and the collected air were measured in a Hopcalite CO meter. Simultaneous determinations of the blood carboxyhaemoglobin (COHb) concentration and the pulmonary elimination of carbon monoxide were performed on 15 full‐term newborns without blood group incompatibility and known haemolytic disease, on 10 infants with jaundice and ABO incompatibility and on 18 infants with Rh haemolytic disease. In all infants the birth weight exceeded 2500 g and none of the infants displayed any clinical signs of respiratory disease. In all groups a significant positive correlation was found between the pulmonary CO elimination and the COHb concentration. The results indicate that in full term newborn infants, the pulmonary CO elimination is efficient from the first day of life even in the presence of haemolytic disease and anaemia. The increased COHb concentrations found in these groups of newborns can thus not be explained by CO retention but should reflect an increased haemoglobin catabolism.