Exercise test using dry air in random adolescents: Temporal profile and predictors of bronchoconstriction

Background and objective Guidelines recommend exercise tests using dry air to diagnose exercise‐induced bronchoconstriction ( EIB ). Lung function changes subsequent to these tests have not been investigated in a general adolescent population, and it remains unknown whether signs of airway inflammation, measured using exhaled nitric oxide ( FeNO ), can predict a positive response. The aim of this study was to investigate the temporal aspect of decline in forced expiratory volume in 1 s (FEV 1 ) after an exercise test using dry air, and to investigate predictors of EIB . Methods From a cross‐sectional study on adolescents aged 13–15 years ( n  = 3838), a random subsample of 146 adolescents (99 with and 47 without self‐reported exercise‐induced dyspnoea) underwent standardized treadmill exercise tests for EIB while breathing dry air. Results Of the adolescents, 34% had a positive EIB test (decline of ≥10% in FEV 1 from baseline) within 30 min. Of the subjects with EIB , 53% showed the greatest decline in FEV 1 at 5 to 10 min (mean decline 18.5%), and the remaining 47% of the subjects showed the greatest decline at 15 to 30 min (mean decline 18.9%) after exercise. Increased FeNO (>20 ppb), female gender and self‐reported exercise‐induced dyspnoea were independently associated with a positive EIB test. Conclusion When assessing general adolescents for EIB with exercise test using dry air, there is a temporal variation in the greatest FEV 1 decline after exercise. Therefore, lung function should be measured for at least 30 min after the exercise. Increased FeNO , female gender and self‐reported exercise‐induced dyspnoea can be predictors of a positive EIB test.