Extended NO analysis in health and disease.

Extended NO analysis is a promising tool in different diseases where NO metabolism is altered. One single exhalation cannot give insight to the NO production in the respiratory system; rather the use of multiple exhalation flows can give the alveolar levels (C(A)NO), airway wall concentration (C(aw)NO) and the diffusion rate of NO (D(aw)NO). Increased values of C(A)NO are shown in COPD, systemic sclerosis, hepatopulmonary syndrome and in severe asthma. In asthma the C(aw)NO and D(aw)NO are increased leading to an increase in bronchial NO flux (J'(aw)NO). Low levels of J'(aw)NO are seen in cystic fibrosis, primary ciliary dyskinesia and in smoking subjects. More studies are needed to evaluate the clinical usefulness of the extended NO analysis, similar to what has been done in systemic sclerosis where a cut-off value has been identified predicting pulmonary function deterioration.