Introduction Investigating airway inflammation and pathology in preschool children is challenging from both a technical and ethical standpoint and as such we urgently need to identify and validate novel, non-invasive techniques. Analysis of exhaled volatile organic compounds (eVOC) has been successfully employed using conventional, offline mass spectrometry in preschoolers (van de Kant 2013). However, real-time, instant analysis of eVOC in this age group would be an important advance in the field of ‘breathomics’. We sought to assess whether real-time online analysis of eVOC was feasible in preschool children attending our hospital.
Methods Breath samples were taken from preschool children (aged between 1 and 6 years) attending the emergency department or an acute medical ward at our hospital. Children breathed room air tidally via a facemask and eVOC were analysed instantly by Proton-Transfer-Reaction time-of-flight mass spectrometry (PTR-Tof-MS) coupled to Loccioni breath collection apparatus. Capnography data was simultaneously recorded. The mass spectra were analysed using a Matlab programme coded for adult patients and the spectra for mass channel (m/z) 59 (acetone) were inspected. Total counts for all mass channels were summated.
Results Eight children (median age 42 months, range 14–59 months) participated, of which five (median age 40 months) were able to produce analysable results. The total median count from the summation of all mass channels was 157,465 ncsp (number of counts per second) ranging from 4,831 to 200,319 ncps. The Figure 1 below demonstrates a spectrum for m/z 59 and capnography trace from one of the participants. The patterns of both traces are comparable.
Discussion The comparability of the traces for the spectrum of m/z 59 and capnography suggests that real-time PTR-ToF-MS is detecting eVOC which relate to end-tidal breathing. The traces are likely offset due to the lag between end-tidal exhalation and the sample reaching the apparatus. This feasibility study has demonstrated that real-time analysis of eVOC is possible in preschool children in an acute setting. Further work is needed to determine the most accurate way of analysing the spectra to be able to apply this novel, non-invasive method of investigating airway inflammation and pathology in preschool children.
Reference 1 van de Kant KD, van Berkel JJ, Jöbsis Q. et al. Exhaled breath profiling in diagnosing wheezy preschool children. Eur Respir. 2013;41:183–8