ObjectiveTo detect the concentration of 8-isoprostane (8-iso-PG) in exhaled breath condensate (EBC) of patients with or at risk for ARDS in ventilation, and investigate its clinical significance.MethodsFifty-five patients with or at risk for ARDS in ventilation admitted between February 2014 and June 2016 were recruited as an experimental group, and simultaneous 30 normal cases were recruited as a control group. Their EBC was collected with EcoScreen condenser. The EBC 8-iso-PG level of the patients between different grades of ARDS (mild, moderate, and sever) or at risk for ARDS was compared, and the correlation of EBC 8-iso-PG with the clinical indicators was analyzed.ResultsThe 8-iso-PG levels in EBC and serum of the patients with or at risk for ARDS in ventilation were higher than those in the control group [EBC: (44.83±11.58) ng/L vs. (19.47±4.06) ng/L; serum: (481.53±444.94) ng/L vs. (19.91±17.60) ng/L] (all P<0.05). The EBC 8-iso-PG of the patients with moderate ARDS (n=15) and severe ARDS (n=7) [(47.18±11.68) ng/L and (50.29±11.06) ng/L] was higher than those with mild ARDS (n=7) or at risk for ARDS (n=26) [(33.04±7.62) ng/L) and (37.17±11.08) ng/L] (all P<0.05). However EBC 8-iso-PG was not different between the patients with mild ARDS and those at risk for ARDS (P>0.05 ). The increased EBC 8-iso-PG could predict ARDS with an area under the receiver operating curve of 0.73. The EBC 8-iso-PG of the patients with or at risk for ARDS was correlated with lung injury score (r=0.418, P<0.01), PaO2/FiO2 (r=–0.378, P<0.05), chest radiograph scores (r=0.410, P<0.05), AaDO2 (r=0.368, P<0.05), and APACHEⅡ score (r=0.718, P<0.05).ConclusionEBC 8-iso-PG can reflect the oxidative stress in lung of ARDS patients in ventilation, and can contribute to the diagnosis and evaluation for moderate and severe ARDS.