Abstract
The measurement of the fraction of nitric oxide (NO) in exhaled air (FeNO) has been a routine examination and a well-defined tool for our differential diagnostic considerations for many years. In contrast, the measurement of NO production in the upper airways (nNO) is a rather exceptional examination with a still debatable benefit.
At present, it is performed more or less only in centres dealing with the diagnosis and treatment of congenital or acquired disorders of the ciliary respiratory epithelium, the so-called ciliary dyskinesias, in which it is significantly reduced. Clinical symptoms of suspected ciliary dyskinesia include recurrent upper and lower respiratory tract infections, chronic secretory otitis, or chronic productive cough.
The European Respiratory Society included in its recommendation the measurement of nNO together with high-speed microscopic video analysis in the first step of the diagnostic proces of congenital (primary) forms of ciliary dyskinesia. Meta-analyzes of clinical studies have proved its high sensitivity and specificity, despite the inconsistency of the critical values used and a significantly lower degree of standardization in comparison to the FeNO.
Due to the rapidity, simplicity and non-invasiveness of nNO measurements as well as due to the ubiquitous nature of the clinical issues leading to its indication, it is appropriate to promote this method to all field specialists who normaly deal with patients suffering from similar complaints.