Does lung contusion affect both the traumatized and the noninjured lung parenchyma? A morphological and morphometric study in the pig.

Isolated unilateral lung contusion (LC) was induced in 12 pigs to determine the pathophysiological role of LC in the high mortality after multiple injury. The Horovitz quotient, pulmonary vascular resistance, mean pulmonary artery pressure, mixed venous oxygen consumption, inspiratory pressure and compliance were significantly decreased in the LC group as compared to controls. The number of polymorphonuclear granulocytes, the microvascular permeability of albumine and the Wilhelmy balance as determined by bronchoalveolar lavage were significantly increased after lung contusion. As indicators of a systemic reaction we found elevated plasma levels of the terminal complement complex and decreased levels of the complement factor 3a after LC. The morphological assessment revealed changes such as those encountered during the early phase of adult respiratory distress syndrome, with granulocyte sticking, endothelial cell adhesion and transendothelial diapedesis. Morphometric analysis demonstrated a significant decrease in alveolar diameter in both the injured and the contralateral lung due to impaired surfactant surface activity. A distinct increase in septal diameter, related to edema and caused by increased microvascular permeability, was found in the injured lungs. These findings emphasize that LC leads to a generalized impairment of the entire lung, which may lead to progressive lung failure.