ULTRASTRUCTURAL STUDY ON THE PULMONARY PARENCHYMA OF THE NEONATES FOLLOWING PROLONGED MECHANICAL VENTILATION

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Abstract
The ultrastructural alterations in the pulmonary parenchyma were studied in four premature babies with the respiratory distress syndrome who were treated by prolonged mechanical ventilation from 43 to 172 days. Macrophages and fibroblasts passed through a defect of the epithelial basement membrane to encompass the hyaline membrane. Thickening and reduplication of epithelial and capillary basement membrane, varying patterns of epithelial regeneration, i.e., hyperplasia of type II pneumocytes and cuboidal cells, and proliferation of fibroblasts and myofibroblasts were observed in the alveolar walls. In the emphysematous areas, elastic fibers were condensed and thickened, or fragmented. All these changes were more pronounced in premature babies, who underwent concentrations of more than 80% of oxygen and high positive end-expiratory pressures (>30 cm H2O) for long periods.