[Diagnosis and classification of pulmonary findings in neonates]

Developmental phases could be defined in neonatal lung tissue fixed in situ or in an ordinary way: glandular lung, canalicular lung with simple tubes covered by cuboid epithelial cells, alveolar lung with usual complicated structure. Canalicular lung could manage the blood saturation which depends on the number of capillaries. There was a different picture of alveoli filled with fluid or air. Hyaline membranes, always occurring in fluid-filled alveoli, represented a barrier for drainage of intraalveolar fluid. Step-wise inflation of lung enabled a histomechanical examination giving lately "functional" figures. They showed a poor functional readiness as well as a quick postnatal adaptability of immature lung. Pressure-volume curves correlated with histological maturity and pathological finding offered a more comprehensive explanation of clinicopathological mechanisms.