Intrapulmonary Instillation of Perfluorocarbon in Experimental Acute Lung Injury Max et al.(page 1437)
Max et al. used an experimental model to induce acute lung injury in 20 pigs to study the effects of partial liquid ventilation (PLV) with perfluorocarbon on the distribution of pulmonary blood flow. Gas exchange and hemodynamic and pulmonary blood flow were assessed in all animals before and after induction of acute lung injury with use of a saline lavage. Then, the animals were assigned randomly to one of two groups: a group of 10 who were submitted to PLV by administering 15 ml/kg of perfluorocarbon through the endotracheal tube at 1 and 2 h after injury, and a group of 10 in whom controlled mechanical ventilation was continued with no changes in respirator settings. Measurements were performed 1 and 2 h after injury in the latter group, as well. At specific points in the study protocol, researchers also injected radioactive-labeled macroaggregates of human serum albumin to enable measurement of pulmonary blood flow using single photon emission computed tomography. With use of specialized software, they generated 12 lung segments (four transaxial slices consisting of ventral, middle and dorsal segments) for each animal to be examined for distribution of blood flow. Arterial carbon dioxide tension increased from 32 ± 4 to 57 ± 13 mmHg after acute lung injury was induced, but, after the initial changes, arterial carbon dioxide tension and pH remained constant in groups 1 and 2. When all 20 pigs, either in gaseous ventilation or in PLV groups, were analyzed together, acute lung injury was shown to cause an increase of pulmonary blood flow to the ventral segment of slice 2 and to the middle segments of slices 1 and 2. Blood flow increased in the combined middle segments but decreased in the dorsal ones. Neither PLV nor gaseous ventilation resulted in a redistribution of blood flow to any of the 12 segments when values at 1 and 2 h after injury were compared with those measured immediately after acute lung injury. In a third group of five pigs, the attenuation control group, a similar number of lung lavages (11 ± 2) were needed to induce acute lung injury with an arterial oxygen tension of 52 ± 14 mmHg. Arterial oxygenation improved significantly after PLV with perfluororcarbon, which may be caused by an improvement in ventilation/perfusion ratios.