MEASUREMENT OF NITRIC-OXIDE IN HUMAN NASAL AIRWAY

The nasal output of nitric oxide (NO) is known to be high, but there h ave been varying reports of the exact level, We attempted to establish a quantitative measurement of nasal NO, and looked for a possible rel ationship with nasal resistance, at rest and during exercise. Nasal ai rway ventilation was performed by using an air pump at a constant flow rate, whilst the soft palate was elevated voluntarily, In a prelimina ry study, the flow rate for sampling was changed and concentrations of NO were measured, After determination of flow rate, rhinomanometry fo r nasal resistance and measurement of nasal NO by chemiluminescence we re carried out before and after moderate exercise. The concentration o f NO ([NO]) exhibited a hyperbolic relationship with flow rate of vent ilation (V'E), indicating [NO] x V'E = net nitric oxide output (V'NO) = constant, Hence, nasal NO was expressed quantitatively as V'NO (nL . min(-1)). For 1 L . min(-1) of ventilation, [NO] varied between 2 and 500 parts per billion (ppb) (mean=323 ppb), The average nasal V'NO in 12 healthy male subjects was 323+/-91 nL . min(-1) (mean+/-SD), After exercise on a treadmill (100, 5 km . h(-1)) for 4 min, nasal V'NO dec reased to 229+/-63 nL . min(-1). At rest, expiratory and inspiratory n asal resistance was 0.27+/-04 and 0.27+/-0.06 Pa . s . cm(-3), respect ively, After exercise, expiratory and inspiratory nasal resistance dec reased to 0.17+/-0.04 and 0.16+/-0.04 Pa . s . cm(-3), respectively. T hese data indicate that nasal NO can be measured quantitatively as V'N O and might be involved in the control of nasal resistance.