Comparison of two porcine acute lung injury models: a post-hoc analysis

Background: Acute respiratory distress syndrome (ARDS) is a common disease in intensive care medicine. Despite intensive research, mortality rates are high, not even in COVID-19 ARDS. Thereby, pigs offer some advantages to study the characteristics of ARDS. Many different ARDS models exist. Most of the articles published focused on histopathological and microscopic lung alterations to identify the most suitable animal ARDS model.Macroscopic observations and descriptions are often missing. Therefore, we performed a post-hoc comparison of two common ARDS models for pigs: lipopoly-saccharide (LPS) vs. a double-hit model (bronchoalveolar lavage +oleic acid infusion). We investigated hemodynamic, spirometric and laboratory changes as another main clinical part of ARDS. Results: The groups were compared by two-way analysis of variance (ANOVA) with a post-hoc Student-Newman-Keuls test. A p value lower than 0.05 was accepted as significant. All animals (n=8 double-hit ARDS; n =8 LPS ARDS) survived the observation period of 8 h. ARDS induction with reduced oxygen indices was successful performed in both models (76 +/- 35/225 +/- 54/212 +/- 79 vs. 367 +/- 64; TO/T4/T8 vs. BLH for doublehit; 238 +/- 57/144 +/- 59 vs. 509 +/- 41; T4/T8 vs. BLH for LPS; p < 0.05). ARDS induced with LPS leads to more hemodynamic (mean arterial pulmonary pressure 35 +/- 3/30 +/- 3 vs. 28 +/- 4/23 +/- 4;T4/18 LPS vs. double-hit; p < 0.05; doses of norepinephrine 1.18 +/- 1.05 vs. 0.11 +/- 0.16; LPS vs. double-hit for T8; p< 0.05) and inflammatory (pulmonary IL-6 expression: 2.41e-04 +/- 1.08e-04 vs. 1.45e-05 +/- 7.26e-06; LPS vs. double-hit; p < 0.05) alterations. ARDS induced by double-hit requires a more invasive ventilator strategy to maintain a sufficient oxygenation (PEEP at T4: 8 +/- 3 vs. 6 +/- 2; double-hit vs. LPS; p < 0.05). Conclusions: Both animal ARDS models are feasible and are similar to human presentation of ARDS. If your respiratory research focus on hemodynamic/inflammation variables, the LPS-induced ARDS is a feasible model. Studying different ventilator strategies, the double-hit ARDS model offers a suitable approach.

Automated summary

This study compares two common ARDS models, LPS and double-hit model, in pigs. The results show that both models can successfully induce ARDS and have similar presentation to human ARDS. However, LPS-induced ARDS leads to more hemodynamic and inflammatory changes, while the double-hit ARDS model requires a more invasive ventilator strategy to maintain oxygenation.