It may provide a very inexpensive method of diagnosing any disease you might be suffering from, researchers say. The breath potentially contains traces of more than 1,000 compounds even though you might see only water vapour coming out of your mouth on a cold winter day.

A team of researchers led by Jun Ye has demonstrated that an optical technique for simultaneously identifying tiny amount of a broad range of molecules in breath has the potential of enabling a fast, low cast screen tool for disease. “It is exciting to imagine the potential of analysing all major biomarkers in one’s breath at once,” says Ye, a physicist at JILA, a joint institute of National Institute of Standards and Technology (NIST) and the University of Colorado at Boulder.

Giving an example, he says nitric oxide can indicate asthma, but it also appears in breath with many other lung diseases, including chronic obstructive pulmonary disease, cystic fibrosis and bronchiectasis.

“However, if we simultaneously monitor nitric oxide, carbon monoxide, hydro-peroxide, nitrites, nitrates, pentane, and ethane, all important biomarkers for asthma, we can be much more certain for a definitive diagnosis of this important disease,” he adds.

Existing methods for detecting trace amounts of molecules from the breath, the researchers say, are either bulky, slow, limited to specific molecules, unable to distinguish very well between multiple compounds or inaccurate at measuring their concentrations. In this new approach, the researchers analyse human breath with “frequency combs,” an optical tool cited in the 2005 Nobel Prize in Physics shared by JILA fellow Jan Hall.

Frequency combs are generated by a laser specially designed to produce a series of very short, equally spaced pulses of light. Each pulse may be only a few millionth billionths of a second long. The laser generates light as a series of very narrow frequency peaks equally spaced, like the teeth of a comb, across a broad spectrum.

In the experiment, researchers report that student volunteers exhaled breath that entered an optical cavity where it was “combed” by the light pulses. By detecting which colours of light were absorbed and in what amounts essentially looking for light absorbed near the “teeth” of the comb, the researchers could detect specific molecules and their concentrations. For example, they say a student smoker who participated in the experiment had a level of carbon monoxide that was five times greater than a nonsmoker in the experiment.

The optical comb approach allows the researchers to simultaneously analyse a very broad spectrum, covering many possible molecular compounds, with high precision, frequency resolution and sensitivity.

But the technique is in early phases, and would require clinical trials before it could become available at a doctor’s office.