Characterization of exhaled nitric oxide: introducing a new reproducible method for nasal nitric oxide measurements

Nitric oxide (NO) is present in the human nasal airways and has been sugges ted to originate primarily from the paranasal sinuses. The aim of this stud y was to establish a new and reproducible method for measurement of nasal N O. Through repeated single-breath measurements the intra- and inter-individual variations of NO levels in nasally (into a tightly fitting mask covering t he nose) and orally exhaled air were determined in healthy humans. Variatio ns due to the methods used were investigated. The contribution of oral NO t o the nasal exhalations by introducing a mouthwash procedure was also studi ed, This study shows distinct individual values of NO in nasally and orally exh aled air of healthy humans. Some diurnal variability was also found with a rise in NO in nasally and orally exhaled air over the day, but no, or littl e, day-to-day variability when comparing the results from separate mornings . There was no correlation between NO levels in nasally and orally exhaled air, whereas there was a strong correlation between NO levels in air exhale d through the left and right nostril. The levels of NO in air exhaled at 0. 17 L.s(-1) through either nostril separately were higher than in air exhale d at the same now rate through both nostrils simultaneously After the intro duction of a mouthwash procedure the level of NO in orally, but not nasally exhaled air was reduced. To conclude the method using nasal exhalation into a nose mask is highly re producible, It is also suggested that subtracting the level of NO in orally exhaled air, after mouthwash, from that in nasally exhaled air, would adeq uately reflect nasal NO levels.