Anyone who has taken an alcohol-breathalyzer test knows what a snitch breath can be.
But those alcohol revelations are just one of the many tales that our exhalations are eager to tell about what’s going on inside of us. Given the right type of test, researchers say, our breath could sing about all sorts of cellular activities, from frantically dividing cancer cells to the toxin-releasing buildup of dangerous bacteria during an infection. “Now we’re starting to discover so many things in breath that we didn’t know were there,” says Dr. Raed Dweik, director of the pulmonary-vascular program at Cleveland Clinic. “Everywhere we look, we’re finding stuff.”
In the latest revelation, researchers from the University of Latvia used an electronic nose to sniff out lung cancer’s unique signature and are hoping to standardize the odiferous pattern for more widespread testing.
That won’t be easy, however, since breath is a potluck of everything that’s emitted by the body. The technology is based on the fact that volatile compounds emitted by cells spill over into the blood, which brings them to the lungs where they are released in the breath. But here’s the challenge — this process is used not only by abnormal cells like tumors, but by normal ones as well, as they go about their daily activities. And it’s also the releasing method of choice for compounds emitted by the billions of bacteria that live in our guts and elsewhere in our bodies, where they act as symbiotic partners in helping us digest food and ward off their more toxic and disease-causing cousins.
“Breath is one of the most complicated mixtures on the planet,” says James Carey, professor of chemistry at the National University of Kaohsiung in Taiwan, who is working on an electronic nose to sniff out bacterial infections — but from the blood.
Dr. Peter Mazzone, director of the lung-cancer program at Cleveland Clinic, admits that such skepticism is justified. Mazzone, who is developing a breath-based test to detect lung cancer, says he needs to consider a number of technical challenges, including the ability to screen out things in the environment that people inhale and could confound the results of a breath test. Then there is the influence of our diet, and the foods that we eat and the compounds they emit as they are digested.
Then there is the hurdle of distinguishing the cancer-specific scents from those of other body processes that may serendipitously occur near a tumor but be unrelated to the cancer process that could skew the results of a breath test as well.
“I think the skepticism is very valid,” he says. But he also points out that in the lab, for example, cancer cells growing in a petri dish emit a distinct profile of volatile compounds that normal cells do not. That suggests that the cancer cells are indeed releasing a chemical fingerprint that is related to the tumor-growing process, and “as a clinician, it’s valuable to understand why that is,” says Mazzone.
Already, doctors rely on breath signatures from heart-transplant patients to detect alkanes, which indicate the organ is being rejected by the host’s immune system and the heart cells are experiencing oxidative damage that forces them to start degrading fatty acids. Anesthesiologists use carbon-dioxide tests to ensure they are placing breathing tubes down the right airway. And doctors can tell if their asthma patients are responding to their medications by testing for the amount of nitric oxide in their breath.
To detect the subtler scent of cancer and certain bacterial infections, some researchers have turned to sharper-sensed beings than ourselves: dogs. Dogs that have been trained to recognize lung cancer, colon cancer and the presence of bacteria like Clostridium difficile suggest that it’s possible to suss out the odiferous signature of diseases. In the lab, scientists have also shown that cultures of cancer cells emit distinctly different vapors above their petri dishes than do normal cells.
If the technology does proves to be reliable and accurate for a wider range of conditions, including cancer and bacterial infections, breath tests could become the next wave of diagnostic tools that come with the biggest advantage of all — they won’t require any poking or prodding, just a deep breath.