Reduced level of nasal nitric oxide (nNO). Current American Thoracic Society/European Respiratory Society (ATS/ERS) guidelines for nNO measurements recommend air aspiration via a nasal probe while the subject exhales through the mouth against resistance in order to maintain velum closure.
Comment:
Nasal nitric oxide (nNO) is measurable in nasal air and found to be low in cystic fibrosis and very low in primary ciliary dyskinesia.