β2-integrin expression on macrophages in the first (a) and final (b) BAL fluid. In the final lavage, the expression of CD11a, CD11b and CD18 was significantly up-regulated (b) in comparison with the values from the first lavage (a), in both groups. However, in the final lavage (b), the levels of up-regulation of CD11a, CD11b and CD18 in the high frequency oscillatory ventilation (HFO) group were significantly lower than those of the conventional mechanical ventilation (CMV) group. The solid column indicates CMV procedure and open column HFO procedure. *P < 0.05 vs CMV-treated. MFI = mean fluorescence intensity (arbitrary units).