Intermittent Alveolar Overdistension for 30 or 240 Minutes Does Not Produce Acute Lung Injury in Normal Pig Lung

Background The objective is to study whether alveolar overdistension can induce acute lung injury in pigs as assessed by analysis of respiratory and histological parameters and inflammatory markers. Materials and methods Experimental study, using mixed-breed pigs. Animals were assigned to one of the following groups: Control Group (CG) ( n = 5), applying mechanical ventilation with tidal volume ( V t ) of 10 ml/kg, respiratory rate (RR) of 18 bpm, and FiO 2 of 1 for 240 min; High V t for 30 min (HVt-30) Group ( n = 5), applying ventilation with V t of 50 ml/kg and RR of 8 bpm and FiO 2 of 1 for 30 min, followed by ventilation as in the CG for a further 210 min; and HVt-240 Group ( n = 5), applying ventilation with V t of 50 ml/kg, RR of 8 bpm, and FiO 2 of 1 for 240 min. Hemodynamic parameters, airway pressures, arterial blood gases, extravascular lung water (EVLW), and cytokines (IL-2, IL-4, IL-6, IL-10, TNF-α, and ITF-γ) in plasma and bronchoalveolar lavage (BAL) were determined. Lungs were fixed with 10% formalin for histological analysis. Results are expressed as mean ± standard deviation. The ANOVA test was used to compare measurements among the three groups. Results At 30 min, airway pressures and oxygenation of HVt-30 and HVt-240 groups were higher than those of controls [P plateau : 39.2 ± 5.6 and 33.0± 5.1 versus 12.2 ± 1.3 ( P 2 /FiO 2 : 443.8 ± 55 and 430.6 ± 34 versus 194.4 ± 77 ( P Conclusions In this animal model, ventilation for 4 h with large tidal volume did not cause ventilator-induced lung injury.