In the direct lung injury, for example, sildenafil treatment decreased a leak of cells, particularly of neutrophils, into the lung, suppressed a release of pro-inflammatory mediators (TNFα, IL-8 and IL-6) and markers of oxidative damage, reduced lung edema formation and apoptosis of epithelial cells, and enhanced respiratory parameters in rabbits with saline lavage-induced model of ALI [168]. Here, TNF is linked to acute respiratory distress syndrome.