Researchers at ETH Zurich and at the University Hospital Zurich now propose to extend such analyses to breath, and in particular to take advantage of modern high-resolution analytical methods that can provide real-time information on the chemical composition of exhaled breath.
The scientists developed an instrument-based version of a principle that has been known for a long time in traditional Chinese medicine: TCM doctors draw conclusions about the health state of a patient based on the smell of the exhaled breath.
It is also known that trained dogs and rats can distinguish the smell of the breath of people suffering from certain variants of cancer.
In these cases the entire smell of the patient`s exhaled breath is gauged, which can give rise to bias.
The scientists, led by Renato Zenobi, professor at the Laboratory for Organic Chemistry, aim at eliminating this bias and identifying the chemical compounds in breath.
Like this, doctors should be able to use specific compounds, which are present in breath at minute concentrations, for medical diagnosis.
Using mass spectrometry, these goals can be reached, as shown in a recent study where the ETH researchers analysed the exhaled breath of eleven volunteers.
They found that the chemical “fingerprint” of exhaled breath, largely based on volatile and semi-volatile metabolites, shows an individual core pattern.
Each volunteer was found to have his/her own characteristic “breathprint”.
Using regular measurements extending over 11 days, the researchers could furthermore show that this metabolic “breathprint” stays constant.
“We did find some small variations during the day, but overall the individual pattern stays sufficiently constant to be useful for medical purposes”, Pablo Martinez-Lozano Sinues, senior scientist in Zenobi`s research group said.
If the measurements would show too large variations, they would not be useful for medical diagnosis.
To carry out these measurements, Zenobi and his colleagues modified commercial mass spectrometers, for example by adding a breath sampling inlet line that delivers exhaled breath from a mouth piece directly into the ion source of the instrument.
Mass spectra showing peaks of roughly 100 compounds in breath can be easily and rapidly obtained in this fashion.
The researchers were able to identify acetone, a product of the sugar metabolism.
Most of the other signals present in the “breathprints” have not been assigned yet, which is something the scientists have on their to-do-list.