There was no correlation between the level of exhaled eicosanoids or FeNO and age, sex, and lung function in any study group. There was no correlation between the different exhaled markers (ie, 8-isoprostane, PGE2, and FeNO) in any of the study groups. There was no correlation between exhaled 8-isoprostane concentrations and ICS dose in those children who were treated with these drugs.
Recently, attention has focused on analyzing EBC for studying the composition of the fluid that lines the respiratory tract. As the measurement of EBC is completely noninvasive, this method is potentially useful for the long-term monitoring of lung inflammation in patients with inflammatory airway diseases, including children.
In this study, we have shown that 8-isoprostane, a marker of free radical-induced lipid peroxidation, is detectable in the EBC of healthy children, indicating that ROS production occurs under physiologic conditions even when there is no evidence of airflow obstruction.
Children with asthma who were steroid-naive and children who had been treated with ICSs had higher exhaled 8-isoprostane concentrations than did healthy children, indicating that lipid peroxidation, which is an important component of oxidant stress, is increased in the lungs of children with asthma. Similar results were reported previously in adults with mild-to-moderate asthma who had increased lung oxidative stress, as indicated by 8-isoprostane levels in EBC.
The concentrations of exhaled 8-isoprostane that we measured in healthy and asthmatic children were higher than those reported in their respective adult counterparts. This discrepancy may be explained partly by the different analytical methods used to measure 8-isoprostane levels in EBC in the two studies (ie, RIA vs enzyme immunoassay). There was a certain degree of overlapping in 8-isoprostane concentrations between healthy children and children with asthma.
This could reflect a different relevance of lipid peroxidation and oxidative stress to the airway inflammatory process in the single child with asthma. For this reason, the measurement of 8-isoprostane in EBC should be considered as part of an integrated assessment of airway inflammation in the single child with asthma.
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