Exhaled nitric oxide measurements in a population sample of young adults.
In epidemiologic studies of asthma there is a group with recent wheeze, but with no airway hyperresponsiveness (AHR), in whom it is unclear whether any significant airway abnormality exists. Exhaled nitric oxide (NO) has been proposed as a measure of airway inflammation. We measured exhaled NO in a population sample of 306 young adults who also underwent bronchial challenge with histamine or a bronchodilator test. Subjects blew into a 3-L Tedlar bag against a 2-mm-diameter resistance to close the soft palate and exclude nasal air. The NO content of expired gas from a single breath was analyzed by chemiluminescent analyzer. Exhaled NO was log-normally distributed in the population sample and duplicate measurements were highly reproducible (intraclass correlation coefficient = 0.98). Exhaled NO correlated significantly with airway responsiveness, measured as the dose-response ratio to histamine (r = 0.39, p < 0.001) and with peripheral blood eosinophils (r = 0.35, p < 0.001). Exhaled NO was significantly greater in asthmatic subjects (geometric mean, 22.2; 95% confidence intervals, 16.1 to 30. 7 ppb) than in normal subjects (7.8, 7.1 to 8.4, p < 0.001) or in subjects with wheeze but no AHR (8.8, 7.5 to 10.3, p < 0.001). We conclude that exhaled NO is log-normally distributed, is highly reproducible and discriminates well among subjects, suggesting that it is both a feasible and useful measurement for epidemiologic studies of asthma. The findings suggest that wheeze in the absence of AHR is unlikely to be associated with airway inflammation.
Salome
C M
CM
Institute of Respiratory Medicine, University of Sydney, Sydney, New South Wales, Australia.
Roberts
A M
AM
Brown
N J
NJ
Dermand
J
J
Marks
G B
GB
Woolcock
A J
AJ
D000328:Adult; D001249:Asthma / Q000175:diagnosis* / Q000503:physiopathology; D001944:Breath Tests; D016535:Bronchial Hyperreactivity; D001985:Bronchial Provocation Tests; D002648:Child; D004305:Dose-Response Relationship, Drug; D005500:Follow-Up Studies; D005541:Forced Expiratory Volume; D006632:Histamine / Q000008:administration & dosage; D006801:Humans; D009569:Nitric Oxide / Q000032:analysis*; D015203:Reproducibility of Results; D012135:Respiratory Sounds
D009569:Nitric Oxide; D006632:Histamine