Short-term and seasonal variations of exhaled and nasal NO in healthy subjects.

Nitric oxide (NO) is an important biological mediator with a variety of cellular and tissue functions. Fractional exhaled (FE(NO)) and nasal NO (FN(NO)) are known to be altered in several respiratory tract disease and disorders. However, there are rather few studies into the reproducibility of FE(NO) or FN(NO) measurements in healthy subjects.