[Pulmonary function in the preterm and full-term newborn during the neonatal period: II. Pulmonary function]

The pulmonary function of 18 preterm neonates weighing less than 1500 g. and of 35 full-term newborn infants weighing more than 2500 g. at birth was measured during the neonatal period. The children were grouped according to their postnatal age (less than 24 h, 24 h- 7 days, and greater than 7 days). The inspiratory and expiratory flow was measured by means of a pneumotachograph and the esophageal pressure by means of a feeding tube filled with distilled water. Lung compliance (CL) was significantly lower in the preterm infants than in full-term infants for all postnatal age groups. However, with relation to body weight (CL/Kg) there were no significant differences. The expiratory lung resistance was higher than the inspiratory resistance in all groups. The work of breathing (Wr) was significantly lower in the preterm neonates than in term infants in all postnatal age groups. Nevertheless, as Wr refers to body weight, there were no significant differences.