Hypoxia depresses nitric oxide output in the human nasal airways

Objectives: The role of oxygen in the nasal air on nasal nitric oxide (NO) output was studied in 13 adult volunteers. Methods: Nasal NO was measured w hile air containing oxygen (0%100% in nitrogen) was aspirated through the n asal airway before and after the topical application of xylometazoline. Res ults: The mean nasal NO output of the untreated nose was 507.8 +/- 161.9 nL /min (mean +/- SD) when 21% oxygen was aspirated through the nasal cavities in series and remained unaltered by 100% O-2 (P =.79). Below 10% oxygen th e reduction in nasal NO output correlated positively and significantly with the decrease in oxygen concentration (r(2) = 0.14). NO output was 245.2 +/ - 153.4 nL/min at 0% oxygen, a significant decline from 21% oxygen (P <.000 1). Nasal vasoconstriction induced by xylometazoline and alterations in the blood oxygen content by a maximal breath-holding or breathing 100% oxygen did not alter nasal NO in hypoxia (P =.41). Conclusions: Nasal NO output is markedly depressed in hypoxia and is oxygen dependent at concentrations of less than 10%. Approximately 50% of nasally generated NO is produced from oxygen in nasal air or regulated by it.