Portable exhaled breath condensate metabolomics for daily monitoring of adolescent asthma

Abstract

Portable methods for measurement and quantification of biological analytes have tremendous promise to advance non-invasive personal health monitoring. Exhaled breath metabolomics shares this promise and has been gaining popularity as a non-invasive technique amenable to a vast range of medical uses. 
 
 This work compares breath metabolite abundances in six healthy control subjects and five asthmatic subjects. Exhaled breath condensate (EBC) samples were collected with a novel miniaturized sampler. This device enables breath sample collection in multiple environments, including intensive care units, outpatient clinics, workplaces, and at home. A total of 293 breath samples were collected and analysed longitudinally, including about 28 samples per subject. EBC was analysed with liquid chromatography-mass spectrometry (LC-MS) to define specific metabolite differences between subjects. Untargeted and targeted metabolomic analyses were performed simultaneously, but with separate data analysis procedures. 
 
 Individual differences among subjects were found longitudinally. When presented by health condition, group differences were enhanced with a clear separation between subjects belonging to either the control or asthmatic group. Unexpectedly, targeted compounds consistently had lower intensities in asthmatics. There is a distinct pattern of a day/night cycle with elevations of peak area values in evening samples. These differences were presented mainly in asthmatic subjects, which can be explained by asthma being a representation of exaggerated amplitudes compared to healthy circadian patterns.
 
 Untargeted and targeted analysis of EBC using this device allows the discovery of novel endogenous metabolic signals in a biological sample and the daily monitoring of selected metabolites related to diseases and medical conditions.&#13.