SERIAL CHANGES IN OXYGEN CONSUMPTION (Vo2) OF INFANTS WITH RESPIRATORY DISTRESS SYNDROME (RDS)2

Abstract

Serial measurements of VO2 in RDS infants made 20 years ago may be dated. Recent developments have allowed us to measure VO2 of infants receiving mechanical ventilatory support. We measured VO2 daily in 14 infants who had RDS. Mean birth weight of these infants was 1.4 (range 0.98 to 2.5) kg, gestational age 31.6 (29-36) wk and 1 min Apgar score 3.0 (1-5). VO2 was measured at 24, 48, 72, and 96 hr postnatal age. We found that VO2 decreased significantly from 8.3±0.9(SE) ml/min/kg at 24 hr to 6.5±0.8 ml/min/kg at 48 hr of age. Thereafter, no statistically significant changes were found (5.5±0.5 ml/min/kg at 72 hr and 5.3±0.6 ml/min/kg at 96 hr). These latter values are within the normal range of healthy pre-term infants. Our results differ from those previously reported wherein VO2 was below normal at 24 hr and then significantly above normal at 96 hr. We conclude that infants with RDS have elevated VO2 in the first 24 hr and approach normal limits in 2-3 days. We surmise that improvements in clinical care, notably the use of mechanical ventilation, have resulted in a change in the patient sampling population and that these results are a reflection of this improved care which has altered the course of the disease. We also have shown that the increased VO2 observed at 24 hr is not directly related to severity of disease and is probably due to a combination of factors including metabolic changes, evaporative heat losses and stress. (This research was sponsored by Thrasher Research Foundation).