Measurement of exhaled nitric oxide is widely used in respiratory research and clinical practice, especially in patients with asthma. However, interpretation is often difficult, due to common interfering factors, and little is known about interactions between factors. We assessed the influences and interactions of factors such as smoking, respiratory tract infections and respiratory allergy concerning exhaled nitric oxide values, with the aim to derive a scheme for adjustment. We studied 897 subjects (514 females, 383 males; mean age+/-standard deviation 34.5+/-13.0 years) with and without respiratory allergy (allergic rhinitis and/or asthma), smoking and respiratory tract infection. Logarithmic nitric oxide levels were described by an additive model comprising respiratory allergy, smoking, respiratory tract infection, gender and height (p0.001 each), without significant interaction terms. Geometric mean was 17.5ppb in a healthy female non smoker of height 170cm, whereby respiratory allergy corresponded to a change by factor 1.50, smoking 0.63, infection 1.24, male gender 1.17, and each 10cm increase (decrease) in height to 1.11 (0.90). Factors were virtually identical when excluding asthma and using the category allergic rhinitis instead of respiratory allergy (n=863). Within each category formed by combinations of these different predictors, the range of residual variation was approximately constant. We conclude that the factors influencing exhaled nitric oxide, which we analyzed, act independently of each other. Thus, circumstances such as smoking and respiratory tract infection do not appear to affect the usefulness of exhaled nitric oxide, provided that appropriate factors for adjustment are applied.

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Allergic occupational asthma is frequent in farming populations. As educational interventions can improve disease management, the short-term effect of an educational intervention in asthmatic farmers was evaluated on the basis of spirometric indices and exhaled nitric oxide fraction (FeNO).Farmers with occupational asthma (n581), mostly sensitised against cow dander and storage mites, participated in a 1-day educational programme. Outcome measures were assessed at baseline and after 4-6 weeks, using FeNO, lung function and a questionnaire. Results were compared with those of a control group without intervention (n524).In the educational group, the proportion of subjects reporting work-related symptoms was reduced after the intervention. The FeNO decreased from a geometric mean of 28.2 to 25.7 ppb, and, in subjects with an elevated (.35 ppb) baseline FeNO (n532), from 59.7 to 49.2 ppb. The corresponding changes in the control group were 25.6 versus 27.7 ppb and 49.5 versus 48.1 ppb. Spirometric results were unaltered in the two groups.Thus exhaled nitric oxide fraction, a marker of allergic airway inflammation, indicated a beneficial effect of a short-term educational intervention in farmers with occupational asthma. This suggests a potential for exhaled nitric oxide fraction in assessing the efficacy of preventive measures within a short time with higher sensitivity than spirometry.

Background: Due to large-scale destruction, changes in membrane diffusion (Dm) may occur in cystic fibrosis (CF), in correspondence to alterations observed by computed tomography (CT). Dm can be easily quantified via the diffusing capacity for nitric oxide (DL NO ), as opposed to the conventional diffusing capacity for carbon monoxide (DL CO ). We thus studied the relationship between DL NO as well as DL CO and a CF-specific CT score in patients with stable CF.

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