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 H(2)O 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: Pa(O) (2) 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.