title: Exercise test using dry air in random adolescents: Temporal profile and predictors of bronchoconstriction.
abstract: 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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Neuroscience/Physiotherapy and Medical Sciences, Respiratory Medicine and Allergology, Uppsala University, Uppsala, Sweden.
authors.forename: Henrik
authors.initials: H
authors.lastname: Johansson
authors.affiliation: Surgical Sciences: Otolaryngology and Head and Neck Surgery, Uppsala University, Uppsala, Sweden.
authors.forename: Katarina
authors.initials: K
authors.lastname: Norlander
authors.affiliation: Women's and Children's Health, Uppsala University, Uppsala, Sweden.
authors.forename: Kjell
authors.initials: K
authors.lastname: Alving
authors.affiliation: Medical Sciences, Clinical Physiology, Uppsala University, Uppsala, Sweden.
authors.forename: Hans
authors.initials: H
authors.lastname: Hedenström
authors.affiliation: Medical Sciences, Respiratory Medicine and Allergology, Uppsala University, Uppsala, Sweden.
authors.forename: Christer
authors.initials: C
authors.lastname: Janson
authors.affiliation: Medical Sciences, Clinical Physiology, Uppsala University, Uppsala, Sweden.
authors.forename: Andrei
authors.initials: A
authors.lastname: Malinovschi
authors.affiliation: Surgical Sciences: Otolaryngology and Head and Neck Surgery, Uppsala University, Uppsala, Sweden.
authors.forename: Leif
authors.initials: L
authors.lastname: Nordang
authors.affiliation: Neuroscience/Physiotherapy and Medical Sciences, Respiratory Medicine and Allergology, Uppsala University, Uppsala, Sweden.
authors.forename: Margareta
authors.initials: M
authors.lastname: Emtner
mesh_terms: D000293:Adolescent; D000388:Air / Q000032:analysis*; D001250:Asthma, Exercise-Induced / Q000175:diagnosis; D016084:Bronchoconstriction / Q000502:physiology*; D003430:Cross-Sectional Studies; D015444:Exercise / Q000502:physiology; D005080:Exercise Test / Q000379:methods*; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D008297:Male; D012119:Respiration; D012737:Sex Factors; D013997:Time Factors
keywords: adolescent; dry air; exercise induced bronchoconstriction test; exhaled nitric oxide; general population