Exhaled breath condensate in intubated neonates- a window into the lung’s glutathione status

Janine M Ward,Courtney Mccracken,Lou Ann S Brown,Theresa W Gauthier,Xiaodu Ping,Katherine Roche,Esther Taylor,Susan Roark,Maria I Rosso

doi:10.1186/1465-9921-15-1

Abstract

BackgroundAnalysis of exhaled breath condensates (EBC) is a non-invasive technique to evaluate biomarkers such as antioxidants in the pediatric population, but limited data exists of its use in intubated patients, particularly newborns. Currently, tracheal aspirate (TA) serves as the gold standard collection modality in critically ill newborns, but this method remains invasive. We tested the hypothesis that glutathione status would positively correlate between EBC and TA collections in intubated newborns in the Newborn Intensive Care Unit (NICU). We also hypothesized that these measurements would be associated with alveolar macrophage (AM) glutathione status in the newborn lung.MethodsReduced glutathione (rGSH), glutathione disulfide (GSSG), and total GSH (rGSH + (2 X GSSG)) were measured in sequential EBC and TA samples from 26 intubated newborns via high performance liquid chromatography (HPLC). Additionally, AM glutathione was evaluated via immunofluorescence. Pearson’s correlation coefficient and associated 95% confidence intervals were used to quantify the associations between raw and urea-corrected concentrations in EBC and TA samples and AM staining. Statistical significance was defined as p ≤ 0.05 using two-tailed tests. The sample size was projected to allow for a correlation coefficient of 0.5, with 0.8 power and alpha of 0.05.ResultsEBC was obtainable from intubated newborns without adverse clinical events. EBC samples demonstrated moderate to strong positive correlations with TA samples in terms of rGSH, GSSG and total GSH. Positive correlations between the two sampling sites were observed in both raw and urea-corrected concentrations of rGSH, GSSG and total GSH. AM glutathione staining moderately correlated with GSSG and total GSH status in both the TA and EBC.ConclusionsGSH status in EBC samples of intubated newborns significantly correlated with the GSH status of the TA sample and was reflective of cellular GSH status in this cohort of neonatal patients. Non-invasive EBC sampling of intubated newborns holds promise for monitoring antioxidant status such as GSH in the premature lung. Further studies are necessary to evaluate the potential relationships between EBC biomarkers in the intubated premature newborn and respiratory morbidities.

Highlights

Analysis of exhaled breath condensates (EBC) is a non-invasive technique to evaluate biomarkers such as antioxidants in the pediatric population, but limited data exists of its use in intubated patients, newborns
GSH status was measureable in both tracheal aspirate (TA) and EBC samples The median volume recovered from the TA was 0.75 ml (IQR: 0.6, 1.75 ml) while the median EBC volume recovered after 30 minutes of sampling was 2.2 ml (IQR: 1.5, 2.5 ml)
GSH, glutathione disulfide (GSSG) and total GSH were detected by high performance liquid chromatography (HPLC) in all samples (100%) in the nM range

Summary

Introduction

Analysis of exhaled breath condensates (EBC) is a non-invasive technique to evaluate biomarkers such as antioxidants in the pediatric population, but limited data exists of its use in intubated patients, newborns. Tracheal aspirate (TA) serves as the gold standard collection modality in critically ill newborns, but this method remains invasive. Current measurements of oxidant stress and inflammation include evaluation of samples obtained from airway lavage, with tracheal aspirate (TA) sampling being the primary site for the premature newborn [10,11]. This standard collection modality remains invasive for routine use in newborns, those born prematurely. Our laboratory has successfully used this method in previous studies to investigate oxidant stress markers in both asthmatic children [18] and adults [19]

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