Towards standardisation in breathomics

Exhaled breath VOCs analysis is safe and non-invasive method of monitoring for human metabolic profiles and has the potential to become diagnostic tool in clinical practise. This thesis first describe in detail the different aspects of exhaled breath VOCs and its use as diagnostic tool in respiratory diseases. The current exhaled breath analysis work-flow including breath sampling, analysis and data processing is also described. A single exhaled breath sample can contain in excess of 500 different chemical species. There is a wide range of factors that can cause the variability to individual breath profiles. In order to detect small changes in breath profiles, a standardised and reproducible approach to exhaled breath analysis methodology is required. The long term storage of exhaled breath samples using multi-sorbent tubes is investigated, the optimum storage protocol and condition is discussed. A portable breath sampling system was also developed for remote sampling. The introduction of this new feature enables breath sampling to be carried out outside the designated laboratory with no location restriction. This feature combined with the easy to use and non-invasive original sampling unit designed for subjects with impaired lung function minimise participant stress level and discomfort. It also utilises the custom developed air supply filtration assembly to create a standardised purified breathable air that can minimise the method variability and improve standardisation to breath samples collected. This methodology is tested in an excise induced bronchoconstriction (EIB) study where two groups of participants: healthy and excise induced bronchoconstriction (EIB) positive undergo high intensity cardiopulmonary exercise testing (CPET). The data from two groups of participants is analysed and three markers which shown correlation with EIB positive participants are determined.