Breath-based tests could benefit from modeling of the underlying biology

Reviewed by James Ives, M.Psych. (Editor)Sep 13 2019

Breath-based tests are gaining in popularity as a non-invasive diagnostic tool for a growing number of medical conditions. Research into improving the collection and analysis of these tests will be presented today at the American Physiological Society (APS) Interface of Mathematical Models and Experimental Biology: Role of the Microvasculature Conference in Scottsdale, Ariz.

In addition to exhaling carbon dioxide, people also exhale trace amounts of various volatile organic compounds (VOCs) that pass from the blood into the lungs as we breathe. Because these VOCs result from metabolic processes, clinicians can gain insight into the processes by analyzing the amount and kind of VOCs in the breath. Such diagnostics can sometimes take the place of much more invasive procedures, such as endoscopy.

Anastasios Angelopoulos, PhD, and his team have observed that the rate at which these VOCs accumulate in the breath varies based on the time that samples are collected. Without accounting for such variation, test results might not be reliable. The team has developed a mathematical model of this time variability by accounting for various physiological mechanisms VOCs encounter. To reach the breath, VOCs pass from the blood into and then out of different tissue types (e.g., vessel walls, lung tissue). Changing properties of these media affect how difficult it is for different VOCs to enter and then leave them. These properties include how likely a particular media is to retain a VOC (its solubility and diffusivity in that media) as well as the relative size of the media.

By taking these factors into account, Angelopoulos says:

Discrepancies in previous studies of the correlations between biomarkers and associated diseases … could be resolved." In addition, through the inclusion of these factors, information from breath tests "turns out to be potentially rich in information pertaining to microvascular and lung health that could otherwise be overlooked."