Open up and say ahhh: new technique uses laser light to analyze breath for diseases

CU-Boulder physics doctoral student Michael Thorpe holds a detection chamber next to a novel laser apparatus at JILA. (Photo: CU)

February 19, 2008 We're familiar with the use of breath testing to determine blood alcohol content, but according to new research the air we exhale could reveal much more about what's happening in our bodies and in the future, breath testing could become a regular part of visiting the doctor. The research by a team of US scientists has shown that markers for diseases such as asthma or cancer can be determined by analyzing trace molecules in the breath using laser light.

The technique called cavity-enhanced direct optical frequency comb spectroscopy was developed by a team of scientists at JILA, a joint institute of the National Institute of Standards and Technology (NIST) and the University of Colorado (CU) at Boulder.

When we inhale, we breathe in a complex mixture of gases including oxygen and carbon dioxide, when we exhale we breathe out a different concoction with less oxygen and more carbon dioxide but also thousands of other molecules in trace amounts. These traces of breath molecules are the ones which could give an indication of disease. For example, traces of ammonia may indicate renal failure whilst elevated acetone levels could suggest diabetes. If these breath molecules are analyzed simultaneously, even more specific information can be collected, for example there if carbonyl sulfide, carbon monoxide, and hydrogen peroxide are all detected with nitric oxide, then this could indicate asthma.

"This technique can give a broad picture of many different molecules in the breath all at once," said Jun Ye, a fellow of JILA and NIST who led the research.

The team conducted a number of experiments on student volunteers and proved they could detect gases such as ammonia, carbon monoxide, and methane on the student’s breath. The students were required to breathe into an optical cavity, a space between two standing mirrors. A pulsed laser was aimed into the cavity, which was designed to bounce the light back and forth. This meant that the entire volume of the cavity could be sampled and by comparing the light entering and exiting the cavity the team could determine which molecules were present in the breath.

This technique has the potential to be an inexpensive, non-invasive and fast method to conduct health screens.

"While current breath analysis using biomarkers is a noninvasive and low-cost procedure, approaches are limited because the equipment is either not selective enough to detect a diverse set of rare biomarkers or not sensitive enough to detect particular trace amounts of molecules exhaled in human breath." Ye said.

"The new technique has the potential to be low-cost, rapid and reliable, and is sensitive enough to detect a much wider array of biomarkers all at once for a diverse set of diseases," he said.

CU-Boulder graduate research assistant Michael Thorpe, Ye, CU-Boulder doctoral student Matthew Kirchner and former CU graduate student David Balslev-Clausen describe the research in a paper that appeared in the Feb. 18 online edition of Optics Express, the free, open-access journal published by the Optical Society of America.

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