For instance: We all exhale a little nitric oxide (NO). But too much nitric oxide is an indicator of lung inflammation, the underlying condition of asthma. Measuring nitric oxide levels in your breath (FeNO, or fractional exhaled nitric oxide) can be useful in testing for and monitoring asthma.
The discovery of this test dates back to the early 1990s, says Kathy Hodgdon, director of marketing for Aerocrine, maker of the device – and its use is widespread. Not only has this test become used around the world, but the International Space Station uses it to test what happens to astronauts’ lungs from inhaling dust and small particles that float around in weightlessness – and to monitor possible airway inflammation before it becomes a health problem. Nitric oxide also plays a role in decompression sickness that may arise from spacewalks.
Clinical practice guidelines from the American Thoracic Society (ATS) give physicians using FeNO testing a standardized way of interpreting results. Raed Dweik, MD, chairman of the ATS committee that developed the guidelines, says, “In patients with non-specific respiratory symptoms, FeNO can help the clinicians determine if they have airway inflammation – a major feature in asthma – or not. In individuals with established asthma, FeNO can help determine how well-treated and controlled – or not – the inflammation is.”
Peter Boggs, MD, the only allergist who was part of the ATS guidelines-writing committee, says the guidelines help physicians tell more clearly if an asthma patient’s inhaled corticosteroid treatment is effective. Since corticosteroid treatment should reduce inflammation, if a person with asthma who’s on such an anti-inflammatory medication still shows above-threshold levels of exhaled nitric oxide, it could indicate that the drug or its dosage needs to be changed, the person isn’t using the inhaler properly, or the person isn’t keeping up with treatments. But it could also indicate that the medication therapy is being overpowered by exposure to environmental allergens and irritants like pet dander or a less obvious trigger.
The testing can help physicians sleuth out the situation, such as for athletes with normal spirometry but high FeNO test results and abnormal symptoms during exercise. The presence of airway inflammation indicates underlying asthma; no inflammation would suggest other factors affecting exercise-induced bronchoconstriction.
Boggs stresses that FeNO testing doesn’t replace other asthma diagnostic tools. “FeNO supports the diagnosis of asthma, it does not make it,” he says. “No single test actually makes the diagnosis; it is a combination of the patient’s medical history, physical findings, pulmonary function assessment, and FeNO. Together, these yield very helpful information.”
Looking ahead, there’s potential for home use of FeNO testing – that’s the visionAerocrine sees for it, according to Hodgdon. But much more study is needed, for instance, of how to read and use test results over time, Boggs says. With those kinds of blanks filled in, and if the testing technology becomes more affordable, “FeNO has the potential to be used in the home setting like peak flow meters are used today,” says Dweik. “It would add information that is not currently measured by peak flow.”
Adapted from “A whole Lot of Hot Air,” by Aaron Marsh; first published in The MA Report, November 2011