It seems that the methods for measurement of nasal NO need to be improved and standardized before we can consider to use this test in monitoring inflammation in AR.

Nitric oxide (NO) is present in the human nasal airways and has been suggested to originate primarily from the paranasal sinuses. The aim of this study was to establish a new and reproducible method for measurement of nasal NO.Through repeated single-breath measurements the intra-and inter-individual variations of NO levels in nasally (into a tightly fitting mask covering the nose) and orally exhaled air were determined in healthy humans. Variations due to the methods used were investigated. The contribution of oral NO to the nasal exhalations by introducing a mouthwash procedure was also studied.This study shows distinct individual values of NO in nasally and orally exhaled air of healthy humans. Some diurnal variability was also found with a rise in NO in nasally and orally exhaled air over the day, but no, or little, day-to-day variability when comparing the results from separate mornings. There was no correlation between NO levels in nasally and orally exhaled air, whereas there was a strong correlation between NO levels in air exhaled through the left and right nostril. The levels of NO in air exhaled at 0.17 L . s -1 through either nostril separately were higher than in air exhaled at the same flow rate through both nostrils simultaneously. After the introduction of a mouthwash procedure the level of NO in orally, but not nasally exhaled air was reduced.To conclude the method using nasal exhalation into a nose mask is highly reproducible. It is also suggested that subtracting the level of NO in orally exhaled air, after mouthwash, from that in nasally exhaled air, would adequately reflect nasal NO levels. Eur Respir J 2000; 16: 236±241.

BackgroundClara cell protein (CC16) is ascribed a protective and anti-inflammatory role in airway inflammation. Lower levels have been observed in asthmatic subjects as well as in subjects with intermittent allergic rhinitis than in healthy controls. Nasal nitric oxide (nNO) is present in high concentrations in the upper airways, and considered a biomarker with beneficial effects, due to inhibition of bacteria and viruses along with stimulation of ciliary motility. The aim of this study was to evaluate the presumed anti-inflammatory effects of nasal CC16 and nNO in subjects with allergic rhinitis.MethodsThe levels of CC16 in nasal lavage fluids, achieved from subjects with persistent allergic rhinitis (n = 13), intermittent allergic rhinitis in an allergen free interval (n = 5) and healthy controls (n = 7), were analyzed by Western blot. The levels of nNO were measured by the subtraction method using NIOX®. The occurrences of effector cells in allergic inflammation, i.e. metachromatic cells (MC, mast cells and basophiles) and eosinophils (Eos) were analyzed by light microscopy in samples achieved by nasal brushing.ResultsThe levels of CC16 correlated with nNO levels (r2 = 0.37; p = 0.02) in allergic subjects.The levels of both biomarkers showed inverse relationships with MC occurrence, as higher levels of CC16 (p = 0.03) and nNO (p = 0.05) were found in allergic subjects with no demonstrable MC compared to the levels in subjects with demonstrable MC. Similar relationships, but not reaching significance, were observed between the CC16 and nNO levels and Eos occurrence. The levels of CC16 and nNO did not differ between the allergic and the control groups.ConclusionsThe correlation between nasal CC16 and nNO levels in patients with allergic rhinitis, along with an inverse relationship between their levels and the occurrences of MC in allergic inflammation, may indicate that both biomarkers have anti-inflammatory effects by suppression of cell recruitment. The mechanisms behind these observations warrant further analyses.

Nitric oxide (NO) is believed to be involved in the pathophysiology of sepsis. This study evaluated the activity of the NO pathway in a human endotoxin model.At baseline and after endotoxin, on-line measurements of exhaled NO (eNO) were made using a chemiluminescence technique with a single-breath method. NO-free air was inhaled prior to exhalation against a resistance. NO in orally and nasally exhaled air and in rectal gas was investigated. Plasma nitrite, nitrate, and guanosine 39, 59-monophosphate (cGMP) and the events after diclophenac administration were also studied.Endotoxin infusion resulted in tachycardia and fever. An early increase in oral eNO concentration was observed and oral eNO decreased after diclophenac administration. NO exhaled nasally, NO in rectum gas and nitrite/nitrate levels remained unchanged over the study period. cGMP increased after 4 h.These findings suggest an early increase in nitric oxide production from the lungs, probably due to increased activity of the constitutive nitric oxide synthase upon endotoxin stimulation. In contrast, nitric oxide production in the upper airways, measured as nasally exhaled nitric oxide and nitric oxide in rectal gas, remained unchanged. Further studies will elucidate if exhaled nitric oxide is a valuable marker of sepsis-induced lung injury and if monitoring of treatment is possible. Eur Respir J 2003; 21: 594-599.

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The gas nitric oxide (NO) is present in high concentrations in human nasal airways. Since NO is known to inhibit the growth of bacteria and viruses, it has been suggested that airborne NO represents the first line of defence against pathogens in the upper airways. Low nasal NO levels have been reported previously in patients susceptible to upper airway infection. Since HIV-positive patients are at risk for respiratory tract infections, including sinusitis, we studied the levels of NO in the upper and lower airways of these patients. A cross-sectional study with age-matched HIV patients and controls was carried out. Nasal and orally exhaled NO were measured in 31 HIV patients and 26 controls using a well-established chemiluminescence method developed for measurements of gaseous NO in the airways. Nasal NO was 21%, lower (p < 0.05, Student's t-test) in HIV patients than in controls, whereas orally exhaled NO did not differ between the two groups. We conclude that nasal NO is reduced in patients with HIV infection. The reduction in nasal NO may contribute to the decreased resistance to airway infections in these patients.

Results from different laboratories indicate that nitric oxide (NO) and carbon monoxide (CO) coexist in the human airways both in health and disease. These gases are present in exhaled human breath and high concentrations of NO as well as CO have been reported in the nasal airways. In addition, exhaled CO and NO are increased in patients with airways inflammation. NO and CO were measured simultaneously in orally exhaled air and in air sampled from the nose in 18 healthy subjects using chemiluminescence (for NO) and infrared (for CO) techniques at different fixed flow rates. The acute effects of smoking on airway release of NO and CO were also studied.Nasal NO was detected in all subjects and the concentrations were highly flowdependent (mean ¡ SEM: 236 ¡ 23 and 527 ¡ 49 parts per billion (ppb), at 2 and 0.5 L?min -1 , respectively). In contrast, no evidence of CO release in the nasal airways regardless of sample flow rate was found. In fact, additional experiments indicated a net absorption of CO when low levels of this gas were flushed through the nasal cavity. Nasal CO also remained undetectable after smoking. Both NO (22¡2 ppb) and CO (1.1¡0.1 parts per million) were consistently found in orally exhaled air. CO, but not NO, levels increased acutely after smoking a cigarette.The authors conclude that the patterns of nitric oxide and carbon monoxide release in the airways seem to differ profoundly in healthy subjects. Orally exhaled air contains both nitric oxide and carbon dioxide whereas nasal air contains nitric oxide only.

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