Expression of biological markers. Real-time polymerase chain reaction analysis of biological markers associated with inflammation (interleukin (IL)-1β, IL-6), fibrogenesis (type III procollagen), and apoptosis (caspase-3). Relative gene expression was calculated as a ratio of the average gene expression levels compared with the reference gene (GAPDH) and expressed as fold change relative to PCV-NS (non-Sigh). Values are mean + standard deviation (SD) of five rats in each group. *Significantly different from PCV non-Sigh (P <0.05); **significantly different from PCV-Sigh (P <0.05); #significantly different from PSV non-Sigh (P <0.05). ALIp, pulmonary acute lung injury; ALIexp, extrapulmonary acute lung injury; PCV, pressure-controlled ventilation; PSV, pressure support ventilation; NS, non-Sigh.