Exhaled nitric oxide in a Taiwanese population: Age and lung function as predicting factors

Background/Purpose: The fractional concentration of exhaled nitric oxide (FE _NO) has been reported to be elevated in asthma and many other lung diseases. The present study investigated reference values and determinants of FE _NO in a Taiwanese non-smoking, healthy adult population. Methods: We used a chemiluminescence analyzer according to American Thoracic Society/European Respiratory Society recommendations to measure FE _NO values in 356 adults who received a health check-up and a detailed respiratory questionnaire at Taichung Veterans General Hospital, Taiwan. Among the volunteers, 249 fulfilled our definition of healthy adults: no history of smoking or physician-diagnosed asthma; no recent upper airway infection; no chronic respiratory symptoms; and no allergic rhinitis and urticaria. Results: Among the 249 non-smoking and non-asthmatic adults, the mean (5 ^th to 95 ^th percentile reference range) FE _NO was 27.9 (12.5-58.0) parts per billion. In multivariate regression analyses, age and lung function (forced vital capacity or forced expiratory volume in 1 second) were associated positively with FE _NO values. Sex, height, weight, and ambient NO values were not associated significantly with FE _NO values. Conclusion: Age and lung function were predictors of FE _NO in this population, and these factors should be considered for clinical applications of FE _NO measurements.