For example, people with diabetes may have fruity or sweet-smelling breath. The odor is caused by ketones, chemicals produced when the body begins to burn fat instead of glucose for energy, a metabolic state known as ketosis.
“The idea that the exhale could hold diagnostic potential has been around for a long time,” said Dr. Davis. “There are reports in ancient Greek and ancient Chinese medical training texts that mention a physician’s use of smell as a way to help guide their clinical practice.”
Modern technologies can detect more subtle chemical changes, and machine learning algorithms can identify the breath patterns of people with certain diseases. In recent years, scientists have used these methods to identify unique “breath tracks” for lung cancer, liver disease, tuberculosis, asthma, inflammatory bowel disease, and other diseases. other. (Dr Davis and her colleagues have even used VOC profiles to distinguish between cells that have been infected with different strains of influenza.)
Before the success of Covid, Breathomix developed an electronic nose to detect a number of other respiratory diseases. “We train our system, ‘OK, this is the smell of asthma, this is the smell of lung cancer. “So it’s building a big database and looking for patterns in the big data.”
Last year, the company – and many other researchers in the field – turned around and started trying to identify a trail for Covid-19. For example, during the initial outbreak of the virus in the spring of 2020, researchers in the UK and Germany collected breath samples from 98 people who visited hospitals with respiratory symptoms. (Participants were asked to exhale into a disposable tube; the researchers then used a syringe to extract a sample of their breath.)
31 of the patients had Covid, while the rest had various diagnoses, including asthma, bacterial pneumonia or heart failure, the researchers reported. Breath samples from people with Covid-19 had higher levels of aldehydes, compounds produced when cells or tissues are damaged by inflammation, and ketones, consistent with research showing that the virus can damage pancreas and induce ketosis.
Covid patients also had lower levels of methanol, which could be a sign that the virus had inflamed the digestive system or killed the methanol-producing bacteria that lived there. Dr Thomas, co-author of the study, said those changes in breathing combined “provide us with the Covid-19 signal”.