(837) Breath Markers of Oxidative Stress in Children With Severe Viral Lower Respiratory Tract Infection

Introduction: Severe viral lower respiratory tract infection (LRTI) forms a major health burden among infants. Infection and associated inflammation induce oxidative stress (OS), which may be aggravated by supportive care in the PICU, together resulting in oxidative injury. There exists little insight, however, in the pulmonary OS status in these patients, particularly during invasive ventilation. This exploratory, prospective study aimed to identify and monitor potential volatile organic compounds (VOCs) of OS during invasive ventilation in children with a severe viral LRTI. Secondary, correlation with ventilator parameters was assessed. It was hypothesized that breath markers of OS mirror clinical improvement in children with severe viral LRTI.

Methods: Exhaled breath from PICU patients ( < 2 years) with severe viral LRTI on invasive ventilation was sampled at up to four time points. Captured VOCs were analyzed by gas-chromatography and mass-spectrometry. Multilevel principal component analysis (PCA) was used to identify key VOCs and their change over time was assessed by paired-Wilcoxon test and a mixed-effects model. Correlation with ventilator parameters was assessed by repeated measures correlation.

Results: In total, 70 breath samples were collected from 21 patients. Multilevel PCA revealed that 15 VOCs were most important to the explained variance (expl. var) of exhaled breath markers (expl. var PC1: 18%, VOCs N=11; PC2: 10%, VOCs N=4). In PC1, the majority of VOCs were straight-chain alkanes and methylated alkanes (N=9), of which 7 significantly decreased from the initial phase of invasive ventilation to the day of planned extubation. Of the other VOCs, 2-ethylhexan-1-ol also decreased over time. The administered oxygen dose did not correlate with any VOC, whereas 6 VOCs, again the (methylated) alkanes, correlated poor-to-moderately with driving pressure.

Conclusions: In this cohort of PICU patients with a severe viral LRTI on invasive ventilation, various straight-chain and methylated alkanes were found to be most important to the variance of exhaled breath markers and mirrored clinical improvement. These VOCs have previously been associated with OS, suggesting that these VOCs could be of value to help monitor the pulmonary OS status.