Relationship between nasal nitric oxide concentration and nasal airway resistance

In the present study the relationship between nasal nitric oxide (NO) concentration and nasal airway resistance (NAR) was investigated in healthy volunteers at rest. Endothelially derived NO is established as a potent vasodilator and as such may be involved in the regulation of the nasal vasculature. Nasal airway resistance is dependent upon the tone of the nasal vasculature. It is therefore suggested that NO may play a role in the regulation of nasal airway resistance. Nasal NO concentration and nasal airway resistance were measured in 123 healthy volunteers. Posterior rhinomanometry was used to obtain the total and unilateral nasal airway resistance. Nasal NO concentration was measured from both the left and the right nostrils, consecutively, during a 20-sec breath hold, using a chemiluminescence gas analyser. NO was measured by sealing a cannula into each nostril consecutively and drawing air through both nasal passages. The results demonstrated that there was no significant difference between the concentrations of NO from the left and the right nostrils (p = 0.7). This indicated that the sampling technique provide a measure of nasal NO which was independent of the side of the nose used for sampling. The mean (+/- s.d) NO concentration sampled from the left nostril was 1,145 +/- 367 ppb. The mean NO concentration sampled from the right nostril was 1,163 +/- 401 ppb. There was a highly significant correlation between the right and left measurements (rho, corrected for ties = 0.95, p < 0.0001). The mean total NAR (+/- s.d) was 0.25 +/- 0.06 Pa/cm3/s. The mean left NAR was 0.50 +/- 0.28 Pa/cm3/s, whilst the mean right NAR was 0.48 +/- 0.31 Pa/cm3/s. There was no significant correlation between total NAR and the left nasal NO concentration (rho = 0.10) or total NAR and right nasal NO concentration (rho = 0.05). Similarly, no correlation was found between the left or right unilateral NAR and left or right nasal NO concentration, respectively. The results of the present study on healthy volunteers demonstrate that the nasal concentration of NO is not related to the total NAR. However, the present study cannot eliminate the possibility that nasal NO may be involved in the regulation of unilateral NAR.