What is exhaled nitric oxide testing?
Asthma symptoms – coughing, wheezing, shortness of breath – are driven by underlying inflammation in the airways. When we want to assess a person’s asthma, we can observe symptoms and test lung function with spirometry, but only recently have we been able to effectively and accurately look at inflammation – by measuring the amount of nitric oxide in a person’s exhaled breath (eNO).
eNO has become an essential part of the three-legged stool we use to assess asthma: symptoms, spirometry (lung function) and exhaled nitric oxide.
These three measurements don’t always correlate with one another, which is why we have to monitor each one. An elevated eNO reflects airway inflammation. This can help with a treatment plan, because regular use of an inhaled corticosteroid lowers the level of exhaled nitric oxide as it reduces inflammation. If levels remain high, it suggests inflammation may still be present, and can signal a need to change treatment plans accordingly.
Being able to measure eNo has been a missing link in diagnosing and monitoring our patients accurately.
David M. Lang, MD, is head of Allergy/Immunology in the Cleveland Clinic Respiratory Institute and co-director of the Asthma Center. Hear a podcast interview with Dr. Lang at www.aanma.org/podcasts or www.allergyandasthmarelief.org.