Spectrum of Oxygen Dependency in Surviving Infants Weighing 600 to 1000 Grams: Decreased Incidence of Severe Chronic Lung Disease

ABSTRACT

Incidence and factors predisposing to chronic lung disease (CLD) were studied in a group of 110 infants still alive at the age of 1 year (69.2%) of an initial group of 159 infants born with a birthweight between 600 and 1000 gm from 1983 to 1988. Low peak inspiratory pressure (PIP), high initial ventilatory rates, slow weaning from respirator and partial arterial oxygen pressure and carbon dioxide pressure values in the range of 40 to 55 torr were used. Oxygen dependency had abimodal distribution with a high number of infants needig oxygen supplement on day 1 (75.9%) and on day 28 (69.1%) compared with 40.3% on day 7, and 37.7% by 8 weeks. When postconceptional age was taken into consideration, 27% of the infants received oxygen supplement at 36 weeks, 10% at 40 weeks, and 3.6% at 44 weeks. Predisposing factors for oxygen dependency at 28 days were low gestational age, respiratory distress syndrome, intermittent positive pressure ventilation (IPPV), air leak, patent ductus arteriosus and oxygen need at 3 and 7 days of life. Conversely, intrauterine growth retardation was found to be the best factor protecting against CLD. Only 7.6% of infants with a gestational age of 30 weeks or more were still oxygen dependent at 36 weeks postconception versus 38.7% and 28% in the group of 24 to 25 weeks and 26 to 27 weeks, respectively. Of the infants 78.1% were intubated and required IPPV; 44.1% were weaned by 4 weeks, 82.5% by 8 weeks, 93% by 12 weeks, and 100% by 15 weeks of life. Eighty-four percent were extubated at the first attempt, suggesting that prolonged ventilation with low PIP is not predisposing to severe lung injury. We conclude that our mode of initial ventilation, using low PIP and high rates, may reduce the incidence of severe CLD. Prolonged need for oxygen is to be expected in the very immature premature infants, without being necessarily a sign of bronchopulmonary dysplasia.