Variations of nasal nitric oxide in a subject with allergic rhinitis: a longitudinal study

Nitric oxide (NO) in the exhaled air is mainly produced by the upper respiratory airway mucosa, and the output of NO has been found to differ from normal in sinonasal disease. In allergic rhinitis (AR) nasal NO output (V(NO)) has been reported to increase compared with healthy individuals. The purpose of this study was to observe daily variations in V(NO) in a subject with AR and to investigate the effect of environmental factors on V(NO).

We measured V(NO) daily in an individual with AR over a period of 5-1/2 months to determine the variability of V(NO) from day to day. We used a 41-year-old, nonsmoking volunteer with AR as our subject to investigate the relationship between V(NO) and some environmental factors likely to affect V(NO). The correlation between V(NO) and nasal symptom scores was also investigated. Daily ambient NO concentrations, humidity, atmospheric pressure, and atmospheric grass pollen concentrations were recorded along with morning nasal NO measurements. At each measurement session, online NO measurements were done from both nostrils at 5 L/min constant transnasal flow. During the study the subject had a short period of a cold and a short period of purulent rhinitis and started using a nasal steroid spray at the end of the study.

V(NO) levels for our subject were higher than previously published values for normal and allergic adults. There was an increase in V(NO) (the highest value throughout the study) in the prodromal period of the cold and a significant decrease (the lowest values throughout the study) during the cold. Change during the purulent rhinitis was less remarkable than change during the cold.

No correlations between environmental conditions (humidity, atmospheric pressure, pollen count) and V(NO) were found. V(NO) changes were also independent of specific and cumulative nasal symptom scores.