Exhaled breath collection and analysis
Exhaled breath was collected using an adjusted ReCIVA® breath sampler
(Owlstone Medical, Cambridge, UK) combined with the CASPER® clean air
supply pump (Owlstone Medical, Cambridge, UK) which provided filtered
inspiratory air to minimize background contamination from ambient air.
Details about the adjustments of the breath sampler can be found in
supplement section 1). The influence of the adjustments to the breath
sampler was assessed separately and the VOC concentrations measured were
similar using both the adjusted and the original sampler (see supplement
section 2). Exhaled breath samples were analysed using thermal
desorption (TD) gas chromatography mass spectrometry (GC-MS) and TD
selected ion flow tube mass spectrometry (SIFT-MS). Details about the
GC-MS and SIFT-MS analysis of the exhaled breath samples are provide in
supplement section 3.