Hydrostatic Versus Oleic Acid-Induced Pulmonary Edema: High-Resolution Computed Tomography Findings in the Pig Lung

Rationale and Objectives. We evaluated the differences between combined hydrostatic and hypervolemic edema and oleic acid-induced edema on high-resolution computed tomography (HRCT) scans. Methods. Twelve anesthetized and ventilated pigs were studied. Hydrostatic edema was induced by ligation of the abdominal aorta and infusion of normal saline (n = 4); permeability edema was induced by intravenous injection of oleic acid (n = 4). Four pigs were studied as normal controls. Serial scans were obtained before and after induction of edema at a constant position in the caudal lobe of the lung. The distribution of edema was assessed visually. Cross-sectional areas (CSAs) of the pulmonary artery and vein were measured both at the lobar and segmental levels. Results. Gravity-dependent opacity, peribronchovascular fluid collection, prominent centrilobular core, thickening of the interlobular septa, and air-space consolidation at the dependent site were the sequential HRCT findings of hydrostatic edema. Randomly distributed, diffuse patchy high attenuation areas with a tendency for predilection in the subpleural and peripheral areas of the secondary lobule were the findings of oleic acidinduced edema. Hydrostatic edema increased the mean CSAs of the lobular vein by 137.8% ± 78.7, but oleic acid edema decreased the mean CSAs by 33.2% ± 22.7. Changes in the mean CSAs of the pulmonary arteries were not significant. The mean vein-to-artery ratio increased significantly in hydrostatic edema but decreased in oleic acid edema. Conclusion. HRCT findings for hydrostatic and oleic acid-induced pulmonary edema differed both in distribution of edema and in pulmonary vascular response.