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.