Nitric oxide accumulation in the nonventilated nasal cavity

Background: Nasal nitric oxide is present in high concentrations in the upp er airway relative to the lower respiratory tract. Objective: To explore the rate of nitric oxide accumulation in the nonventi lated nasal cavity. Methods: In 9 healthy subjects previously trained to close the soft palate, steady-state plateau nitric oxide levels were recorded while air was aspir ated through the nasal airway in series at a constant flow rate. Nitric oxi de was then allowed to accumulate in the nasal cavity by occluding both nar es and keeping the velum closed. After varying occlusion times, peak nitric oxide levels and a second plateau were ascertained. Results: While the subjects aspirated air at a constant flow, there was a s low rise to a first nitric oxide plateau. On opening to the analyzer after the accumulation period, the peak nitric oxide level was several times high er than the initial plateau (range, 2810-19 008 ppb) and then slowly return ed to previous plateau levels. There was no significant difference between initial and second plateau nitric oxide levels for any period. The accumula ted nitric oxide peak increased in direct proportion to the accumulation ti me (P<.001). Conclusions: Nitric oxide concentrations accumulate in the nonventilated na sal cavity in proportion to the time of nonventilation. Peak nasal nitric o xide values after accumulation are similar to published sinus nitric oxide measurements obtained by direct puncture. These results suggest an importan t alternative source of nitric oxide in humans.