Artificial ventilation of premature newborn rabbits: effects of positive end-expiratory pressure on lung mechanics and lung morphology.

44 premature newborn rabbits, removed by hysterotomy on day 27 of gestation, were ventilated with positive pressure under differing standardized conditions, with or without application of positive end-expiratory pressure (PEEP; 5 cm H2O). After 10 min ventilation, compliance of the lung-thorax system was significantly higher in fetuses ventilated with PEEP than in controls. The application of PEEP also resulted in a significantly lower maximal expiratory air flow compared to controls in groups ventilated with standardized tidal volume. Morphometric evaluation revealed bronchiolar epithelial lesions to be less prominent in fetuses treated with PEEP. Our findings show that application of PEEP has a beneficial effect on lung mechanics during artificial ventilation and that it reduces the risk of epithelial damage to the airways, presumably by promoting uniform expansion of the lung parenchyma.