Our breath may be as unique as our fingerprint. Compounds in exhaled air produce a unique and stable molecular autograph or "breathprint" – one that could be used to monitor disease or track response to medication.
Renato Zenobi at the Swiss Federal Institute of Technology in Zurich and his colleagues discovered breathprints by analysing the breath of 11 healthy individuals. The team did this four times a day over nine days, and used a technique called mass spectrometry to identify the molecules in each breath sample.
The team was interested in metabolites, compounds produced by the body's metabolism. The molecules are volatile and small enough to pass from the blood into airways via the alveoli in our lungs, so are present in our breath – albeit in miniscule amounts, sometimes less than one molecule per billion molecules of air.
The team found that metabolites in individuals' breath remained "constant and clear", says Zenobi. "Our genomes are unique, our epigenomes are unique, our microbiomes are unique, so it is not surprising our breath metabolomes are also unique," says Jeremy Nicholson from Imperial College London, who was not part of the team.
"What is important is how they vary from individual to individual and how they differ in relation to development of disease or in response to therapy." Zenobi's team can identify compounds in breath immediately, so our breathprint could be used to detect signature metabolites associated with disease, giving an instant diagnosis.
In a preliminary study, Zenobi has shown that breath samples can reveal whether people have chronic obstructive pulmonary disease. The clever part of the work is that they use a special scheme to selectively charge the trace amounts of volatile compounds, which provides results quicker than other types of gas chromatography, says Patrik Spanel from Keele University, UK, who was not part of the study.