EFFECTS OF PARTIAL LIQUID VENTILATION ON LUNG INJURY IN A MODEL OF ACUTE RESPIRATORY-FAILURE - A HISTOLOGIC AND MORPHOMETRIC ANALYSIS

Objective: To compare the histopathologic changes observed in a sheep model of oleic acid induced acute respiratory failure during partial l iquid ventilation with perflubron with gas ventilation. Design: Random ized, controlled study. Setting: Animal laboratory and pathology labor atories of a university hospital, Subjects: Fourteen healthy adult she ep, weighing 64.9 +/- 6.4 kg, Interventions: Lung injury was induced w ith oleic acid (0.15 mL/kg). A tracheostomy tube was inserted, along w ith systemic and pulmonary artery monitoring catheters, Animals were r andomized to undergo either partial liquid ventilation (n = 7) or gas ventilation (n = 7). Animals underwent euthanasia at the end of the 90 -min study period, after which the endotracheal tube was clamped with the lungs in expiratory hold at a positive end-expiratory pressure of 5 cm H2O. En bloc excision of the heart and lungs was performed by tho racotomy. Perfusion of the isolated lung vasculature with 2.5% parafor maldehyde and 0.25% glutaraldehyde in a 0.1-M phosphate buffer was per formed, Histologic analysis followed. Measurements and Main Results: G as exchange increased markedly in the animals that underwent partial l iquid ventilation compared with the gas-ventilated animals (PaO2 at 90 mins: gas ventilation treatment group, 40 +/- 8 torr [5.3 +/- 1.1 kPa ]; partial liquid ventilation-treatment group, 108 +/- 60 torr [14.4 /- 8.0 kPa]; p=.004). Lung histologic analysis demonstrated a better o verall diffuse alveolar damage score (partial liquid ventilation-treat ment group, 12.4 +/- 1.4; gas ventilation-treatment group, 15.0 +/- 1. 7; p=.01). In the partial liquid ventilation-treatment group, we obser ved an increase in mean alveolar diameter (partial liquid ventilation- treatment group, 82.4 +/- 2.9 mu m; gas ventilation-treatment group, 6 7.7 +/- 3.9 mu m; p=.0022) and a decrease in the number of alveoli per high-power field (partial liquid ventilation-treatment group, 25.7 +/ - 0.9, gas ventilation-treatment group, 31.4 +/- 2.5; p=.0022), in sep tal wall thickness (partial liquid ventilation treatment group, 6.0 +/ - 0.6 mu m; gas ventilation treatment group, 8.3 +/- 1.0 mu m; p=.0033 ), and in mean capillary diameter (partial liquid ventilation treatmen t group, 13.0 +/- 0.8 mu m; gas ventilation treatment group, 19.9 +/- 1.4 mu m; p=.0022). Conclusions: Partial liquid ventilation is associa ted with notable improvement in gas exchange and with a reduction in t he histologic and morphologic changes observed in an oleic acid model of acute lung injury.