Pulmonary excretion of carbon monoxide in the human newborn infant as an index of bilirubin production: III. Measurement of pulmonary excretion of carbon monoxide after the first postnatal week in premature infants.

Using a single pass, flow-through system, the excretion rate of endogenously produced carbon monoxide (VeCO) was measured as an index of bilirubin production in 41 Caucasian infants of various gestational ages after the first postnatal week. twenty-one were less than or equal to 32 weeks gestation. The mean slope for the 25 premature infants with multiple VeCO determinations was -0.21 +/- 0.11 (SE) microliters/kg/hour per day (P less than .025, one-tailed). Fifteen premature infants with at least three VeCO determinations during the first 30 days of life had an average decrease in total CO excreted of 1.33% per day compared to the extrapolated initial value of total CO excretion of 27.0 +/- 2.0 (SE) microliters/hour, giving a calculated maximum red cell life span of 75 days.