257 Malondialdehyde in Plasma and Exhaled Breath Condensate Collected from Ventilated Infants

Abstract

Aim: Malondialdehyde (MDA) is a product of lipid peroxidation that is a marker of oxygen free radical damage. The aim of our study was to measure MDA in exhaled breath condensate (EBC) collected from ventilated infants and to use it as a marker of oxidative stress in the lungs of these patients. Methods: MDA concentration was determined by high-performance liquid chromatography in plasma and EBC collected from 17 ventilated infants with humidification. In 11 infants, blood was taken at the same time as EBC collection. FiO2, alveolar-arterial oxygen difference (AaDO2), mean airway pressure (MAP), oxygenation index (OI) and peak inspiratory pressure (PIP) were recorded at the time of sample collection to estimate potential oxidative stress to the lungs, and correlated with MDA concentration. Results: The detection limit for breath condensate MDA was 0.0015 micromolar. MDA was measurable in breath condensate in 13 patients, but was below the detection limit in 4 patients. Median MDA concentration was 0.004 (range: 0 − 0.022) micromolar in EBC. Median MDA plasma concentration was 0.375 (range: 0.054 − 5.171) micromolar. Plasma MDA concentration was strongly correlated with both FiO2 (r squared=0.22; p=0.008) and AaDO2 (r squared=0.28; p=0.006), and weakly correlated with MAP (r squared=0.14; p=0.04). There was no relationship between plasma MDA and either OI or PIP. Although we found a significant correlation between the concentration of MDA in plasma and in EBC (r squared=0.32; p<0.03), EBC MDA concentration did not significantly correlate with FiO2, MAP, PIP or OI. Conclusion: Our results suggest that MDA concentration in plasma correlates with oxidative stress of the lungs of ventilated infants. Although MDA can be measured in EBC collected from ventilated infants, even during humidication, and correlates with MDA concentration in plasma, the amounts are very low and normalisation to EBC electrolytes may be necessary.