Exhaled nitric oxide in the diagnosis and management of bronchial asthma: From bench to bedside?

The identification of nitric oxide in exhaled breath and its role as a surrogate marker of eosinophilic inflammation of the airways led to rapid development in the area of its measurement. Standardized measurement techniques have been developed as well as simple, cheap, and reliable equipments. Although a number of factors have been identified as affecting its assay, fractional exhaled nitric oxide (FENO) can reliably be used to distinguish eosinophilic from non-eosinophilic airway inflammation. Unlike the other indirect measures of airway inflammation such as FEV1 reversibility and bronchoprovocative tests, FENO is noninvasive and gives a direct measure of inflammation. There are sufficient data supporting its role in the diagnosis of asthma, monitoring of disease, prediction of relapse, and level of compliance. Measurement of FENO has therefore made the transition from the bench to the bedside. Of recent, there are attempts at devising interpretative strategies for its use in day to day clinical practice.