Research in the field of exhaled breath analysis is developing rapidly and is currently focussed on disease diagnosis and prognosis. The ability to identify early onset of life-threatening diseases, by a subtle change in exhaled profile that is picked up through a non-invasive measure, is of clinical interest. However, implementation of exhaled breath analysis can extend further beyond disease diagnosis and/or management. Using a non-invasive and rapid sample collection with high sensitivity, breath analysis may be seen to have potential benefit to the wider community. This research describes preliminary investigations into exhaled breath in exercise-based scenarios that aims to translate current breath analysis methodologies into a sport and exercise medicine context.
An adaptive absorbent-based breath sampling methodology was used to collect a total of 220 breath samples from 54 participants over 3 studies. Breath volatiles were analysed using thermal desorption-gas chromatography-mass spectrometry. Data were analysed with targeted, and multivariate metabolomics-based approaches.
Potential health impacts to high performance and recreational swimmers exposed to chlorinated water was studied. Following preliminary and scoping studies, 19 participants were sampled before a 30 min swim, and a further 5 times for 10 hrs after swimming. Environmental and control samples were also collected. Concentrations of chlorine-based disinfection by-products were observed to increase by up to a median of 121-fold, and take up to 8.5 hrs to return to pre-swimming levels. Metabolomic profiling identified the monoterpene geranylacetone to be a discriminant variable in samples taken 10 hrs after swimming. Geranylacetone is associated with membranes and extracellular fluids and an upregulated trend was observed across the five sampling time points post-swimming. Further research with an appropriately stratified and powered cohort (n=38) was recommended.
The effects of intense exercise on breath profiles was explored for the possible use of breath analysis for exercise science with elite performance-based medicine. Twenty-nine participants provided exhaled breath samples before undergoing a maximal oxygen uptake (fitness) test and then provided 2 additional samples over the following 1 hr period. High and low fitness groupings, deemed by oxygen uptake values, were compared for exhaled metabolites. Lower exhaled acetone and isoprene were observed in participants with greater absolute oxygen uptake leading to a hypothesis for a non-invasive breath based fitness test.
Finally, an interface for breath-by-breath analysis using a transportable mass spectrometer was developed. A controlled change in exhaled profiles was achieved through the ingestion of a peppermint oil capsule. Menthone was measured on-line and monitored for up to 10 hrs post-administration. Sixteen participants enabled the system to be demonstrated as exhaled menthone was at elevated concentrations for at least 6 hrs. Validation against thermal desorption-gas chromatography-mass spectrometry confirmed the system to be detecting metabolites at the sub-µg L-1 range.
A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.