CHRONIC OXYGEN DEPENDENCY IN INFANTS BORN AT 24-32 WEEKS GESTATION - THE ROLE OF ANTENATAL AND NEONATAL FACTORS

Objectives: To study the incidence of chronic oxygen dependency (COD) among ventilated survivors born at 24-32 weeks gestation from 1986 to 1994 and to identify antenatal and neonatal factors that may have chan ged with time; and to identify antenatal and neonatal factors that cou ld contribute to the development of COD in infants born at 24-32 weeks gestation using a case control model. Methodology: Infants born at 24 -32 weeks gestation in one tertiary referral centre between 1986 and 1 994 and admitted to the neonatal intensive care unit for respiratory s upport were studied. Data accumulated prospectively since 1986 in surv ivors of ventilation were analyzed to identify antenatal and neonatal factors that could have changed with time. The cohort of infants who d eveloped COD were matched for gestation and time of birth with a contr ol group of infants who did not have COD. Significant factors that cou ld have contributed to the development of COD were identified using fo rward logistic regression analysis. Results: The number of mothers adm itted for threatened premature labour (TPL), and pregnancy induced hyp ertension decreased with time while the use of antenatal steroids and maternal antibiotics increased. More infants were delivered by Caesare an section during the later years. There was an increase in neonatal s epticaemia with time while there were decreases in hyaline membrane di sease, pneumothorax, pulmonary interstitial emphysema, use of high pea k inspiratory pressures (PIP) and high inspired oxygen. The incidence of COD decreased. The case controlled study revealed a significant pos itive association between COD and male gender, birthweight less than t he 10th percentile for gestation, PIP over 30 cm H2O, septicaemia and significant patent ductus arteriosus (PDA) requiring indomethacin. The re was a negative association with TPL. Conclusions: Further decrease in COD can be achieved only if septicaemia, PDA and the use of high PI P can be avoided, The most effective way of reducing the incidence of COD is by reducing the incidence of prematurity.