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 (FEV1) 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 FEV1 from baseline) within 30 min. Of the subjects with EIB, 53% showed the greatest decline in FEV1 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 FEV1 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. In a general adolescent population, we investigated the bronchoconstriction profile to exercise challenge test using dry air ventilation to diagnose EIB. Half of the subjects with EIB had their greatest decline in FEV1 within 10 min after exercise while the other half had a more delayed response (15–30 min).