Continuous tracheal gas insufflation during partial liquid ventilation in juvenile rabbits with acute lung injury

To examine the hypothesis that combined treatment with tracheal gas insufflation (TGI) and partial liquid ventilation (PLV) may improve pulmonary outcome relative to either treatment alone in acute lung injury (ALI), saline lavage lung injury was induced in 24 anesthetized, ventilated juvenile rabbits that were then randomly assigned to receive (n = 6/group) 1) conventional mechanical ventilation (CMV) alone, 2) continuous TGI at 0.5 l/min, 3) PLV with perfluorochemical liquid, and 4) combined TGI and PLV (TGI + PLV), and subsequently ventilated with minimized pressures and tidal volume (Vt) to keep arterial Po(2) (Pa(O(2))) >100 Torr and arterial Pco(2) (Pa(CO(2))) at 45-60 Torr for 4 h. Gas exchange, lung mechanics, myeloperoxidase, IL-8, and histomorphometry [including expansion index (EI)] were assessed. The CMV group showed no improvement in lung mechanics and gas exchange; all treated groups had significant increases in compliance, Pa(O(2)), ventilation efficacy index (VEI), and EI, and decreases in PaCO(2), oxygenation index, physiological dead space-to-Vt ratio (Vd/Vt), myeloperoxidase, and IL-8, relative to the CMV group. TGI resulted in lower peak inspiratory pressure, Vt, Vd/Vt, and greater VEI vs. PLV group; PLV resulted in greater compliance, Pa(O(2)), and EI vs. TGI. TGI + PLV resulted in decreased peak inspiratory pressure, Vt, Vd/Vt, and increased VEI compared with TGI, improved compliance and EI compared with PLV, and a further increase in Pa(O(2)) and oxygenation index and a decrease in PaCO(2) vs. either treatment alone. These results indicate that combined treatment of TGI and PLV results in improved pulmonary outcome than either treatment alone in this animal model of ALI.