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Exhaled Nitric Oxide

Exhaled nitric oxide attempts to provide information regarding inflammation, but in the end, measurement of exhaled nitric oxide tells the physician only what the exhaled nitric oxide is. The physician then must rely on summary study data to then make the leap of faith that the eNO in this patient correlates to a certain amount of inflammation. This remains quite a leap. Although certainly a helpful tool, exhaled NO assays will not supply the magic answer for the titration of lung disease therapies. It will not tell us when leukotriene antagonists might be particularly beneficial, nor whether our dose of inhaled steroids is sufficiently suppressing cellular inflammation. It will not advise us whether proton-pump inhibitors might be helpful.

However, exhaled NO can be useful as part of an overall process of data collection about a patient. For example, a low eNO in a steroid-naïve patient with presumed asthma does call into question the diagnosis. In such a patient, the physician should consider vocal cord dysfunction, cystic fibrosis, ciliary dyskinesia, airway tumors or papillomas, external compression of the airway, etc etc.