Comparison of two exhaled biomarkers in children with and without sleep disordered breathing

Objective: Airway oxidative stress and inflammation are likely to be involved in sleep disordered breathing (SDB) in children. We aimed to measure concentrations of 8-isoprostane (8-IsoP) in the exhaled breath condensate (EBC) and exhaled nitric oxide (FENO) in patients with SBD and healthy children, in order to assess the relationship between these two biomarkers, disease severity, and overnight changes. Methods: Patients with SDB (n = 46) and healthy controls (n = 20) aged 4.5–15.1 years (M/F: 36/30) underwent exhaled measurements. Patients with SDB underwent standard polysomnography to define primary snoring (PS: AHI < 1) and obstructive sleep apnea (OSA). Upon awakening the following morning, FENOwas measured and EBC was collected for the measurement of EBC 8-IsoP. Results: OSA patients yielded higher awakening levels of 8-IsoP in EBC than PS patients and control subjects. The 8-IsoP levels, though not FENO, correlated with AHI (r = 0.40, p = 0.003) and SaO2 (r = −0.50, p = 0.001). Cut-off levels of 8-IsoP predicted OSA with a high AUC value (0.84, p = 0.000). Sensitivity and specificity for 8-IsoP levels above the percentile 50 (33.3 pg/mL) were 76.5% and 78.1%, respectively. 8-IsoP levels did not change from the evening to morning session, whereas morning FENOlevels rose significantly only in patients with mild OSA (p = 0.03). Conclusion: Levels of 8-IsoP, though not FENO, distinguish children with OSA from those with PS or healthy, correlate with disease severity and closely predict OSA in the whole sample.