Objective: To evaluate protective effect and its mechanism of prone position ventilation (PPV) combined with recruitment maneuver (RM) as a lung protective ventilation strategy on oleic acid-induced acute respiratory distress syndrome (ARDS) in dogs.
Methods: Twenty-four oleic acid-induced ARDS dogs were ventilated with volume controlled ventilation (VCV): 16 cm H2O (1 cm H2O=0.098 kPa) of positive end-expiratory pressure (PEEP) and 10 ml/kg of tidal volume (VT). All dogs were randomly divided by random digit table into four groups: supine position (SP group), prone position (PP group), supine position+RM (SPRM group), and prone position+RM (PPRM group, 6 in each group), and ventilated by VCV for 4 hours and then sacrificed by exsanguination. The serum levels of inflammatory mediators were measured respectively at 0.5, 2 and 4 hours. After they were sacrificed, the levels of cytokines in left lung tissue homogenate were measured. The wet/dry weight ratio of right lung was determined and histological sections of the lungs were prepared and examined.
Results: (1) At 4 hours, interleukin-8 (IL-8) in serum in the SPRM group was significantly higher than in other three groups (all P<0.05), tumor necrosis factor-alpha (TNF-alpha) in serum in the SPRM group was significantly higher than in the PP group and the PPRM group (all P<0.05). (2) IL-8 in lung tissue homogenate of the dorsal aspect of the lung in the SP group was higher than in the PP group and the PPRM group (both P<0.05). TNF-alpha in lung tissue homogenate at the dorsal aspect of the lung in the SPRM group was higher than in the PP group and the PPRM group (both P<0.05). (3) Wet/dry weight ratio of right lung in the PP group and the PPRM group were significantly lower than that in the SP group and the SPRM group (all P<0.05). (4)Pathology score of lung tissue at the dorsal aspect of the lung in the PP group and PPRM group was significantly lower than in the SP group and the SPRM group (all P<0.05).
Conclusion: Protective ventilation strategy combined with RM is safer in prone position than supine position, and it alleviates lung injury in dog with ARDS.