Correlation between nitric oxide content in exhaled breath condensate and the severity of acute respiratory distress syndrome

Nitric oxide (NO) can induce necrosis and detachment of branchial epithelium, aggregate inflammation and induce acute respiratory distress syndrome (ARDS). The detection of NO in exhaled breath condensate (EBC) has not been widely applied in evaluating ARDS condition. This study thus tested NO in EBC of ARDS patients, in order to provide non-invasive method to monitor disease condition of ARDS. ARDS patients in ICU of our hospital were recruited in parallel with healthy controls. NO contents in EBC and serum were measured in both control group and ARDS patients before/after treatment, and between survived and dead patients. APACHE II score, PaO₂/FiO₂, and PaO₂ were also quantified and analyzed for their correlation with NO contents. Correlation between EBC and serum NO contest was also analyzed. ARDS patients had significantly higher EBC/serum NO contents before treatment compared to control. NO levels were remarkably decreased after treatment (P<0.05). Survival patients had decreased APACHEII score, and EBC/serum NO, plus elevated PaO₂/FiO₂, and PaO₂ after treatment. Dead patients had elevated APACHEII score, EBC/serum NO with prolonged treatment, plus decreased PaO₂/FiO₂, and PaO₂ (P<0.05). EBC/serum NO in ARDS patients were positively correlated with APACHE II score, and negatively correlated with PaO₂/FiO₂, and PaO₂ (P<0.05). NO level in EBC was positively correlated with serum level in ARDS patients (P<0.05). The detection of EBC NO content can reflect hypoxia and disease condition of ARDS patients, and benefits treatment efficacy evaluation and prognostic judgement. EBC NO can replace serum NO due to satisfactory correlation.