Prevalence of EILO Among Children With Asthma

The goal of this cross-sectional study is to investigate the prevalence of Exercise Induced Laryngeal Obstruction (EILO) in children with asthma.

The hypothesis is that the prevalence will be around 15%, which is higher than the prevalence of 5-8% among the general adolescent population. This is based on the increased prevalence of EILO among adult asthmatics.

Participants who are referred for an Exercise Challenge Test will perform an additional Continuous Laryngoscopy during Exercise Test with expiratory FEV1 curves, and fill in the Borg scale for dyspnea, Asthma Control Test, EILODI questionnaire and DISCO-RC questionnaire.

Background:Exertional dyspnoea is a common and limiting symptom within the paediatric population. Regular physical activity is paramount for the development of children since it not only promotes cardiorespiratory fitness and muscle strength, but also offers opportunities for self-expression, building confidence and social interaction and integration. It is therefore important to identify the correct cause(s) of exertional dyspnea and reverse them to enable children to be active without symptoms.

Exercise induced bronchoconstriction (EIB) is a well-known cause of exertional dyspnoea and is highly specific of childhood asthma. Another less recognized cause of exertional dyspnoea is exercise induced laryngeal obstruction (EILO). EILO is an inappropriate closure of the larynx during strenuous physical activity with no obvious laryngeal pathology at rest, limiting airflow and causing inspiratory stridor. It can co-exist with and mimic symptoms of EIB.

Previous studies showed a prevalence of 6% in adolescent populations). However, recent studies revealed a much higher prevalence ofEILO in adults with asthma, up to 25-47%. The prevalence of EILO amongst children with asthma has not yet been investigated. In this study, the aim is to investigate the prevalence of EILO in children with asthma.

If EILO is a significant comorbidity of childhood asthma this would implicate that EILO screening should be considered when exercise is a persistent trigger of symptoms in asthmatic children. Correct EILO diagnosis and treatment can lead to adequate treatment of EILO, and to prevention of overtreatment of asthma.

Methods: Participants who are referred for an Exercise Challenge Test will perform an additional Continuous Laryngoscopy during Exercise Test with expiratory FEV1 curves, and fill in the Borg scale for dyspnea, Asthma Control Test, EILODI questionnaire and DISCO-RC questionnaire.

Power analysis: The sample size is calculated based on an estimated prevalence and confidence interval, with a power of 80% and alpha of 0.05. When estimating a prevalence of 15% (CI 10-20%), which is 2 times higher than in the general population (30), this results in a sample size of 196 participants. This was rounded to 200 participants. Dropouts will be replaced until a total number of 200 participants completed both the ECT and CLE test.

Statistical analysis for primary outcome: The prevalence of EILO in the study population of adolescents with asthma will be calculated as a percentage with a 95% confidence interval. Baseline characteristics will be compared between participants and non-participants of the CLE test. If there are no significant differences between these groups, it can be assumed that participants represent the studied population. If there are significant differences in baseline characteristics, we will examine the correlation of these characteristics with EILO. An estimated prevalence of EILO will be calculated among the non-participants based on these correlations, and an estimated weighted average will be calculated of the prevalence of EILO among the studied population.

Eligibility Criteria:
Inclusion Criteria:

* Age 12 to 18 years
* Paediatrician diagnosed asthma confirmed with at least one of the following during the last two years: Positive ECT (post-exercise fall in FEV1 \> 10%) / Positive methacholine test (PC20 value of ≤8 mg/mL) / Bronchodilator reversibility (increase in FEV1 ≥12% and/or ≥200 mL following inhalation of 200-400 μg short-acting β2-agonists)

Exclusion Criteria:

* Other severe cardiopulmonary disease
* Inability to perform ECT or CLE test
* Inability to perform technically acceptable spirometry
* Asthma exacerbation or respiratory tract infection in the last 2 weeks
* Short-acting β2-agonists or long-acting β2-agonists use less than respectively 8 and 24 hours before the ECT or CLE test
* Oral corticosteroid use in the 4 weeks before the ECT or CLE test