Apart from the physical alveolar disruption induced by MV, researchers realized that it was excessive lung volume which leads to overdistention of the lung, i.e., volutrauma, characterized by hyperpermeability of the alveolar-capillary barrier
. A classical experiment found that pulmonary edema and cellular ultrastructural abnormalities were encountered only in rats subjected to high V[sub]T but not in those in which lung distention was limited by thoracoabdominal strapping, which highlighted the effect of transpulmonary pressure instead of airway pressure during VILI.
Moreover, the alveolar epithelium damage will lead to an increase in the permeability of the alveolar-capillary barrier
, which in combination with changes in hydrostatic and oncotic pressures, might lead to the formation of pulmonary edema.,