Ventilator-associated lung injury superposed to oleic acid infusion or surfactant depletion: histopathological characteristics of two porcine models of acute lung injury.

BACKGROUND: The pathophysiological concept of acute lung injury (ALI) in combination with ventilator-associated lung injury (VALI) is still unclear. We characterized the histopathological features of intravenous injection of oleic acid (OAI) and lung lavage (LAV) combined with VALI.
METHODS: Pigs were randomized to the control, LAV or OAI group and ventilated by pressure-controlled ventilation. MEASUREMENTS INCLUDED: haemodynamics, spirometry, blood gas analysis, lung wet-to-dry weight ratio (W/D), total protein content in broncho-alveolar lavage fluid (BALF), and lung pathological description and scoring.
RESULTS: Five hours after lung injury induction, gas exchange was significantly impaired in both the OAI and the LAV groups. Compared to controls, we found an increase in W/D and histopathological total injury scores in both the LAV and OAI groups and an increase in BALF total protein content in the OAI group. In contrast to the LAV group, the OAI group showed septal necrosis and alveolar oedema. Both groups exhibited dorsal and caudal atelectasis and interstitial oedema. In addition, the OAI group demonstrated a propensity to dorsal necrosis and congestion whereas the LAV group tended to develop ventral overdistension and barotrauma.
CONCLUSIONS: This study presents a comparison of porcine OAI and LAV models combined with VALI, providing information for study design in research on ALI.