Effects of distention of the preterm fetal lamb lung on lung function with ventilation

Constant distending pressure when applied to the immature fetal lamb lung was reported to improve compliance and prevent the subsequent development of the respiratory distress syndrome after delivery. These experiments were designed to repeat those observations and identify the mechanism(s) responsible for the effects of constant distending pressure on subsequent lung function. The compliance of the lungs of exteriorized fetal lambs at 130 to 133 days gestational age increased 2.5-fold after 1 h of 15 cm of distending pressure. However, subsequent ventilation of the lambs exposed to distending pressure and control lambs resulted in comparable sequential compliance and blood gas and pH measurements. Severity of lung disease as reflected by the peak inspiratory pressure needed to normalize PCO2 values decreased as surfactant-saturated phosphatidylcholine pool sizes increased (r values > 0.90) and minimum surface tensions of alveolar washes decreased, but the distention procedure did not change these relatio...