Exhaled nitric oxide comes of age

The measurement of exhaled nitric oxide (NO) made its way as a new lung function from basic discovery to clinical application in less than a decade. As was the case with spirometry, after the initial bloom of the field, making and following basic discoveries, contradictory findings and unexpected discoveries brought the area to a halt, and scientists have been prompted to take a fresh look at all of the available data and the future horizon. The following four articles on this topic in this issue provide a cutting-edge update of recent developments and interpretation of our current understanding of the field. International experts accepted our invitation to contribute to this dedicated section and to cover those areas where there have been major changes in recent years. The paper by Le-Dong et al provides an exciting summary of methodological challenges, advances and recent technological developments on the measurement of FENO in small animal models. It summarizes data using these measurements in discovering many different functions of NO signalling in the respiratory field. Recent discoveries concerning measurement of FENO in chronic obstructive pulmonary disease (COPD) and their implication in phenotyping and treating the disease are expertly summarized by Arthur Gelb and colleagues, while Robin Taylor provides a clinically oriented overview on the appropriate placing of FENO as a biomarker in clinical decision making. Moving beyond single FENO measurements, the promises and pitfalls of extended FENO analysis are carefully addressed by Marieann Högman. All authors provided not only a state-of-the-art summary but also gave a personal viewpoint to their writing. We hope their approach will facilitate your enthusiasm to share your personal opinion, or perhaps critical view, openly with the research community. We can work together to identify and plan future research focusing on additional studies that are now needed to clarify the unsettled issues in this field, and can identify new areas of research for the future. Since FENO is in the vanguard of breath analysis, we recommend this special section to anyone interested in exhaled biomarkers and biomarker-based clinical decision making, and hope that you enjoy reading these excellent reviews as much as we did.