Background

This study aims to compare the use of variable mechanical ventilation with conventional mechanical ventilation in a porcine model of ARDS induced by oleic acid.

Methods

The animals were divided into two groups (n = 6), Conventional Ventilation (CO) and variable ventilation with Bi-Oscillatory PEEP (BiPEEP). ARDS was induced using intravenous oleic acid (0.15 mL.kg^-1). After, the animals were evaluated during 180 minutes and, measurements were taken every 30 minutes until the end of the observation period. The animals in the CO group were then ventilated under controlled pressure (Tidal Volume target at 6 mL.kg^-1) and 5cmH2OPEEP. Variable ventilation was characterized by the oscillation of PEEP from 5 to 10 cm H2O every 4 respiratory cycles. Ventilatory, hemodynamic parameters, oxidative stress, antioxidant enzymes, Interleukin 8 (IL8) and 17-a (IL17a) were evaluated. Histological samples were collected from the upper and the lower portion of the left lungs and analyzed separately.

Results

BiPEEP improved lung compliance and PaO2 in comparison to control (p < 0.05). The levels of oxidative stress and antioxidant enzymes showed no significant difference. There was no difference in IL17a between groups. IL8 was significantly increased in the lung base of CO group in relation to BiPEEP group and it was reduced in the apex of BiPEEP group in comparsion to COgroup. The BiPEEP group showed less changes in histopathological patterns.

Conclusions

Variable ventilation with bi-oscillatory level of PEEP demonstrated a potential ventilatory strategy for lung protection in an experimental model of ARDS.