Effect of positive end-expiratory pressure on inflammatory response in oleic acid-induced lung injury and whole-lung lavage-induced lung injury

Purpose. The present study investigated the effects of positive end-expiratory pressure (PEEP) on the inflammatory response in two different lung injury models: edematous lung induced by oleic acid (OA); and atelectatic lung induced by whole-lung lavage (LAV). Methods. Japanese white rabbits (n = 28) were allocated to one of the two lung injury (OA or LAV) groups, and each group was treated with intermittent positive pressure ventilation, using zero end-expiratory pressure (ZEEP) or PEEP (1 cm H2O above the lower inflection point [LIP]). Thus, the animals were divided into LAV-ZEEP, LAV-PEEP, OA-ZEEP, and OA-PEEP groups. Blood and bronchoalveolar lavage fluid (BALF) were sampled 3 h after ventilatory treatment to analyze interleukin (IL)-8 levels. Results. Rio, was significantly decreased after the induction of lung injury, but was significantly higher in the PEEP groups compared to the ZEEP groups for each lung injury. Serum IL-8 levels were elevated in both experimental models. Serum IL-8 levels were significantly lower in LAV-PEEP than in LAV-ZEEP, whereas no difference was noted between OA-PEEP and OA-ZEEP. BALF IL-8 levels were lower in LAV-PEEP than in LAV-ZEEP. PEEP above LIP attenuated the elevation of IL-8 in BALF and serum, in atelectatic lungs, but did not attenuate these increases in the edematous lungs. Conclusion. These results suggest that the protective effects of PEEP on injured lungs may depend on the underlying lung pathology.