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.
Institute of Respiratory Medicine, University of Sydney, Sydney, New South Wales, Australia.
C M
CM
Salome
A M
AM
Roberts
N J
NJ
Brown
J
J
Dermand
G B
GB
Marks
A J
AJ
Woolcock
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