Measurement of nitric oxide in human nasal airway

Abstract

The nasal output of nitric oxide (NO) is known to be high, but there have been varying reports of the exact level. We attempted to establish a quantitative measurement of nasal NO, and looked for a possible relationship with nasal resistance, at rest and during exercise.Nasal airway ventilation was performed by using an air pump at a constant flow rate, whilst the soft palate was elevated voluntarily. In a preliminary study, the flow rate for sampling was changed and concentrations of NO were measured. After determination of flow rate, rhinomanometry for nasal resistance and measurement of nasal NO by chemiluminescence were carried out before and after moderate exercise.The These data indicate that nasal NO can be measured quantitatively as V 'NO and might be involved in the control of nasal resistance. Eur Respir J., 1996, 9, 556- [6]. However, quantitative measurement has been performed in only a few studies on exhaled NO [7,8] and nasal NO [9]. In the nasal airway, NO was first detected by ALVING et al. [2] (1993). These authors found that most exhaled NO comes from the nose because of some 10 fold higher concentration of nasal NO than of exhaled NO. In general, a concentration of a gas rising from the wall of the lumen should vary with the amount of ventilation. Accordingly, the concentration of exhaled NO has been reported to correlate hyperbolically with a ventilatory volume, whereas the net output of NO (V'NO) remained constant [8]. We applied the same method in attempting to establish a quantitative measurement of the nasal airway NO, and investigated the relationship between nasal airway NO and the nasal resistance before and after exercise. Materials and methods Subjects and protocolTwelve male subjects (aged 27-35 years), with no allergies or abnormal rhinoscopic findings, volunteered for this study. The protocol of the study was reviewed and approved by the Asahikawa Medical College Institutional Review Board for Research. Subjects rested in a sitting position for at least 15 min, during the last 5 min of which rhinomanometry and the measurement of nasal airway NO were performed. Subjects then walked on a 10°graded treadmill at 5 km·h -1 for 4 min. Immediately after exercise, subjects sat down and the measurements were repeated. RhinomanometryThe anterior method of rhinomanometry [10] was applied to obtain nasal resistance of each side of the nasal airway. From the flow-pressure curve obtained by rhinomanometry (model SR-11, Rion, Japan), nasal resistance at 100 Pa was taken as the nasal resistance value (Pa·s·cm -3 ) for each subject. The total nasal resistance for both nasal airways was obtained by calculating the sum of the reciprocals of parallel resistance for each nasal airway. Measurement of nasal airway NOThe quantitative measurement of NO in the human exhaled gas has already been established [8]:

Inhibition of nitric oxide synthase by nasal decongestants

“…NO seems to play a pivotal role in these physiological functions as amongst others it has been shown that NO is involved in the regulation of the vascular tone in the nasal mucosa [25,30]. By this means NO is thought to modulate nasal vascular conductance and nasal cavity volume, which are correlated to the nasal airway resistance [16,17]. It should be noted however, that recent investigations, using high flow rate insufflation, contradict the existence of such a relationship [31,32].…”

“…In addition, the exact localization of NOS in nasal mucosa has been identified [14,15]. Furthermore, NOS activity seems to be involved in nasal vascular conductance and in nasal cavity volume [16,17]. Also NO, upon reaction with the superoxide anion radical and forming peroxynitrite, has been shown to act as potent cytotoxic effector molecule [18].…”

Exhaled and nasal nitric oxide measurements: recommendations. The European Respiratory Society Task Force

“…Exhaled and nasal NO are markedly flow-dependent, and a significant reduction in NO concentrations has been reported when sampling or exhalation flow rates increase [5,10,13,31,39,40]. The probable reason for the reduction in NO concentration with increased expiratory or sampling flow is that the same amount of NO will be dispersed in a different exhaled or sample volume.…”

“…Nasal NO measurements are also flow-dependent [40], and the importance of the dilution of nasal NO with the air from the lower airways cannot be overestimated. Thus, mean(±SEM) nasal NO levels in healthy children when sampled from the nose during tidal breathing through the mouth were 239±20 ppb, and were only 21±9.1 ppb during tidal nasal breathing [14].…”

“…However, the first exhalation fraction is usually associated with a transient NO peak ( fig. 2), which represents the portion of exhaled air most contaminated with the nasal [40,42], oropharyngeal and ambient NO in the dead space. The detection of this peak depends on the response time of the analyser, and should be discarded from the analysis, unless there is a particular need to analyse NO in this part of exhalation.…”