Fig. 3. Concentrations of the cytokines tumor necrosis factor α (TNF-α), interleukin 8, and growth-related oncogene α (GRO-α) measured by enzyme-linked immunosorbent assay in the plasma of the animals at baseline, just before injection of saline or lipopolysaccharide in the mechanically ventilated groups (MV-saline and MV-LPS) or of lipopolysaccharide in the spontaneously breathing group (SB-LPS), and then 1 and 4 h after injections. Significant changes over time in each group were assessed by repeated-measures analysis of variance followed by the  post hoc Student–Newman–Keuls when significance was reached. Asterisks indicate significantly different values as assessed by the post–analysis of variance comparisons. ***  P < 0.001  versus baseline. Crosses indicate significant differences between groups at the same time. +  P < 0.05, ++  P < 0.01, +++  P < 0.001 for MV-saline  versus the other groups. ns = not significant.