Biomarker levels per group at two time points. Levels of surfactant protein D (SP-D), Clara cell protein (CC16), KL-6 and soluble receptor for advanced glycation end products (sRAGE) in patients without lung injury at onset of mechanical ventilation (no lung injury) and ALI/ARDS patients (ALI/ARDS), ventilated with either lung-protective mechanical ventilation (open boxes) or potentially lung-injurious mechanical ventilation (grey boxes). In each group, the left bar represents T = 0 hours, the right bar represents T = 48 hours after inclusion. Box plots represent 25th, 50th and 75th percentile; whiskers represent values within 10th and 90th percentile; "°" represent outliers and "*" represent extreme outliers. # P < 0.05 for difference in absolute values between groups at baseline; ‡ P < 0.05 for difference in increases over time between groups.