Nasal nitric oxide and the nasal cycle

Objectives. To establish the relationship between nasal patency and the nit ric oxide (NO) concentration in the nasal airways. Methods. Unilateral nasa l NO concentration (n = 11) and inhaled nasal NO concentration at oropharyn x (n = 9) were measured in healthy adult volunteers. Subjects breathed norm ally through the nose with a known resistance (ranged from none to total oc clusion) placed in one nostril. In a subgroup (n = 7), the unilateral nasal NO concentrations were determined with nasal cavity congestion induced by lateral decubitus. Results. When the added nasal resistance was less than 6 cm H2O per liter per second, the peak NO concentrations in the nose remain ed below 80 parts per billion (ppb). Thereafter, the higher the resistance, the greater the NO concentration. It was up to 1109.7 ppb when the front n ostril was totally occluded. There was no correlation between oropharyngeal NO concentrations and resistance in the front of the nose (r = 0.4). There was a significantly negative correlation between nasal cavity volumes and nasal NO concentrations (r = -0.8, P < .001). Conclusions. Increases in nas al resistance to levels encountered in the nasal cycle and in recumbency au gments the NO concentration within the obstructed side of the nose. Althoug h that within the nose changes with patency, the NO concentration is consta nt down to the lower airways. The modulation role of the upper airways to t he inhaled NO concentration remains unclear.