[Measuring airway inflammation in clinical practise - application and interpretation]

Airway inflammation plays a major role in the pathology of both asthma and COPD and is the target of corticosteroid treatment. In daily routine practise, however, airway inflammation is still not often considered by pneumologists to support the diagnostic process or to aid in disease management, despite studies showing that patients could benefit. Eosinophilic airway inflammation is of special interest, as it is not restricted to allergen-induced airway diseases, and because it generally responds well to anti-inflammatory treatment with corticosteroids. Therefore, the early detection of this kind of underlying inflammatory process can have a positive impact on finding a diagnosis as well as for disease management. The non-invasive detection of eosinophilic airway inflammation using induced sputum is too time consuming and therefore too expensive in outpatient settings. As sputum eosinophils correlate with the concentration of exhaled nitric oxide (FeNO), its measurement could serve as a more economic alternative, especially as new small handheld analysers are available now, that allow the rapid FeNO analysis, even in children. This review will cover some basics and technical aspects of FeNO measurements, which should be known to correctly interprete results in clinical practise. In the second part, the clinical value and the limits of FeNO measurements, as well as the potential interpretation of results are discussed based on recently published literature.