[Pulmonary adaptation of the newborn infant: in relation to respiratory distress syndrome].

At onset of respiration, important changes occur in the pulmonary circulation of the newborn. Pulmonary blood flow increases tenfold and pulmonary arterial pressure decreases quickly, thereby decreasing pulmonary vascular resistance to less than 5% of the prenatal values. Right-to-left shunting through the ductus arteriosus and the foramen ovale ceases concomitantly. About 100 ml of alveolar liquid are removed from the alveolar space by active and passive transport. Most of this fluid is drained by the pulmonary bloodstream. Both, disorders in the circulatory adjustments or a prolonged clearance of alveolar liquid, result in an interstitial oedema and hence can contribute to the development of respiratory failure in the newborn.