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, FENO was 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 FENO levels 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.