Measurement of Nasal Nitric Oxide

Abstract

The major part of nitric oxide (NO) in exhaled air originates from the nasal airways, with only minor contribution from the lower airways and the oral cavity. The physiological role of the very high local NO concentration in the paranasal sinuses is still unclear. The most widely used and best-standardized method to sample nasal NO in isolation from the lower respiratory tract is aspiration at a fixed flow through the nasal passages in series. Important technical considerations include the choice of the correct transnasal flow and the ability of children to perform a breath-holding manoeuvre.The effects of age and height on nasal NO values have yet to be defined in a larger population of healthy children using the recommended aspiration technique. Presently, there is no validated technique available to measure nasal NO in infants and small children.The measurement of nasal NO concentrations has evoked interest in its potential to serve as a non-invasive and simple diagnostic tool for upper and lower respiratory tract disorders. Measurements of nasal NO concentrations are helpful to screen children with clinical symptoms suggestive of primary ciliary dyskinesia and to exclude this disease in those with high nasal NO concentrations with high certainty. Nasal NO measurements are, however, of no diagnostic utility in distinguishing between other conditions such as asthma, cystic fibrosis, bronchiectasis, sinusitis or rhinitis, or in monitoring therapeutic interventions in any such disorder.