Fig. 4. Concentration of the cytokines interleukin 8 and growth-related oncogene α (GRO-α) in the bronchoalveolar lavage (BAL) performed at the end of the experiment in animals injected with lipopolysaccharide while mechanically ventilated ( closed bars ) or breathing spontaneously ( open bars ) and in mechanically ventilated animals injected with saline ( dashed bars ). Nonparametric analysis of variance on rank test (Kruskal–Wallis test) showed significant differences among the three groups for both cytokines ( P < 0.05). Asterisks indicate significant post hoc test results. ** P < 0.01, *** P < 0.001 versus the two other groups. Tumor necrosis factor α is not represented because its median was at zero value in all groups.