[Lung mechanics in premature infants with severe respiratory distress syndrome]

Serial pulmonary function tests were performed in 13 preterm infants with severe RDS and 16 premature neonates with healthy lungs (8 intubated because of hypovention after birth, 8 were breathing spontaneously). Airflow was measured by a pneumotachograph, pressure changes were determined by airway pressure in ventilated infants or esophageal pressure in spontaneously breathing neonates. Pulmonary mechanics were calculated by a computerized system (PEDS/Medical Associated Services, Hatfield, Pennsylvania). In mechanically ventilated infants with RDS dynamic compliance of the respiratory system was low during the first 6 days. On Day 7-10 there were higher values for infants who could be extubated within the first 10 days compared to those, who had to be ventilated for more than 10 days. In the course of the disease, improvement in gas exchange preceded increase of compliance. Intraindividual comparisons in the acute and recovery phase of RDS and in infants with normal lungs showed higher values for compliance and lower values for airway pressure and resistance during spontaneous breaths. The differences between dynamic compliance of the respiratory system measured during mechanical ventilation, and dynamic lung compliance recorded during spontaneous breaths are due to influences of the respirator on the infant's lung.