Measuring exhaled nitric oxide in COPD: from theoretical consideration to practical views

There is good evidence that FE_NO increases with an exacerbation irrespective of the initial low or high baseline value. However, there is insufficient evidence to establish a fixed cutoff value for elevated FE_NO in COPD today. Instead, a personal baseline FE_NO level should be established when the patient is in a stable phase of the disease, which will subsequently set high and low FE_NO levels in a personalized manner. In the future, home monitoring of FE_NO could help identify exacerbations early, allowing proper action to be taken.