Exercise-induced laryngeal obstruction (EILO) is one of many different causes for adolescents to experience dyspnoea during exercise. Objective exercise-testing with continuous video laryngoscopy is crucial for a correct diagnosis since it is difficult to differentiate EILO from other exercise related conditions in the airways only on the symptomatology. The main symptom in EILO is inspiratory stridor arising from an obstruction at the laryngeal level during ongoing exercise which quickly resolves after the exercise has stopped. EILO is often misdiagnosed as exercise-induced bronchoconstriction (EIB), which is obstruction in the peripheral airways that typically arises after cessation of exercise. From a previous survey investigating self-reported exercise-induced dyspnoea in all 12-13-year-old adolescents in Uppsala (n=3,838, response rate 60.2%) a subset of 150 randomly selected adolescents (103 with dyspnoea and 47 controls) performed standardized treadmill exercise-tests for EIB and EILO. During the exercise-test for EIB the subjects breathed dry air according to the current recommended guidelines. EIB was defined as a decrease in FEV1 ≥10% from baseline. EILO was diagnosed during a continuous laryngoscopy exercise (CLE) test by use of the CLE-score method and was defined as an obstruction of grade 2 at either glottic or/and supraglottic laryngeal level. The estimated prevalence of EIB in the general population was 19.2% and the estimated prevalence of EILO was 5.7%. No gender differences were detected. A diagnostic software program for EILO, EILOMEA, was compared with the CLE-score and the methods were found to be compatible. EILOMEA was used to map and compare laryngeal response patterns in adolescents with exercise-induced dyspnoea (EIB and/or EILO), in adolescents with dyspnoea but without a diagnosis of EIB or EILO, and in healthy controls, all of whom had performed the CLE-test. No differences were seen between the healthy controls and the adolescents with dyspnoea without a diagnosis. Only adolescents diagnosed with EILO showed a significant different laryngeal response pattern which strongly suggests that the diagnostic procedure is reliable. In a follow-up study of patients referred for investigation of exercise-induced dyspnoea, we investigated the outcome of surgical vs. conservative treatment of EILO-positive subjects and subjects tested negative for the diagnosis, regarding the level of exercise-induced dyspnoea and physical activity. Surgically treated patients had less breathing problems and were more physically active than both conservatively treated patients and patients who were tested negative.

Experiencing respiratory symptoms in conjunction with exercise is common in children and adolescents and can have a negative impact on daily life. The aim of the thesis was to estimate the prevalence of exercise-induced dyspnoea, exercise-induced bronchoconstriction (EIB) and exercise-induced laryngeal obstruction (E-ILO) in a general adolescent population, and to explore factors associated with EIB. Methods: All 12-13-year-old adolescents in the city of Uppsala (n=3,838) participated in a survey on exercise-induced dyspnoea. A subsample of adolescents who answered the survey, 103 randomly selected adolescents reporting exercise-induced dyspnoea and 47 random adolescents who did not report exercise-induced dyspnoea underwent standardised treadmill exercise tests for EIB and E-ILO. The exercise test for EIB was performed while breathing dry air; a positive test was defined as a decrease ≥10% in FEV1 from baseline. E-ILO was investigated using continuous laryngoscopy during exercise. Health related quality of life (HRQoL), and objectively measured daily physical activity were investigated in those with (n=49) and without (n=91) a positive EIB-test. Results: The prevalence of exercise-induced dyspnoea was 14%, and the estimated prevalence of EIB and E-ILO in the total population was 19.2% and of 5.7%, respectively, with no gender differences. In adolescents with exercise-induced dyspnoea 40% had EIB, 6% had E-ILO, and 5% had both conditions. An increased baseline level of fraction of nitric oxide in exhaled air (FeNO), female gender, and exercise-induced dyspnoea were associated with a positive EIB test. Female adolescents with EIB had lower HRQoL and lower baseline lung function compared to females without EIB. These differences were not observed in male adolescents. There was no difference in time spent in moderate- to vigorous daily physical activity between adolescents with and without EIB.