Can a Breathalyser Detect Diseases?

Most people have heard of the breathalyser as the tool police use to check whether drivers have been drinking. Breathalysers estimate the amount of alcohol in a person’s breath. They work by using a simple chemical redox reaction — ethanol is converted into acetic acid at an anode and oxygen is reduced at the cathode. A microprocessor converts the electric current generated into a blood alcohol level — although this reading is only an estimate and the actual level must be measured on a blood sample.

But breathalysers offer so much more than capturing over-the-limit drivers. And in a recent paper in the journal ACS Nano, scientists have diagnosed seventeen diseases from analysing exhaled breath. The results in the paper — Diagnosis and Classification of 17 Diseases from 1404 Subjects via Pattern Analysis of Exhaled Molecules — show just how revealing our breath can be.

Breathe in — breathe out

Doctors have used exhaled breath to detect diseases for almost 2500 years. They have known that certain components in our breath — volatile organic compounds or VOCs — are linked to diseases. It wasn’t only breath that doctors had to smell either — in ancient times it was the physicians job to smell the urine and excrement of the noblemen’s infants.

The use of VOCs relies on the fact that a whole array of relatively low molecular weight VOCs undergo changes due to changes in the body — in this instance we are interested in the changes due to diseases. Many experiments have been carried out measuring VOCs from various bodily fluids using headspace analysis, chromatography and mass spectrometry. Headspace analysis is also used in other types of analysis as discussed in the article, The Benefits of GC/MS Coupled with a Headspace Trap to Monitor Volatile Organic Compounds in the Production of Beer.

Measure the exhaled breath

But exhaled breath is the easiest to sample — being non-invasive — and is the most useful source of bodily VOCs for monitoring our health. Our exhaled breath contains the usual suspects — nitrogen, oxygen and carbon dioxide — that we learn about in school, but it also contains very small concentrations of 100s of other compounds. And it is these compounds that give away how we are feeling as the amount of each substance varies depending how well you are.

The paper in ACS Nano describes how the scientists used artificial intelligence to classify and diagnose seventeen different diseases by determining the chemical composition of a person’s breath. The researchers collected over 2800 breath samples from over 1400 people who had one of seventeen different diseases. The researchers found that each disease has a unique fingerprint based on thirteen VOCs.

The team suggest that the results show that an inexpensive, portable breathalyser could be used to screen for any of the diseases covered in a simple, non-invasive way.

Coming to a policeman soon?