More Relaxation by Deep Breath on Methacholine

Study Overview
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Brief Summary
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Deep inhalation (DI) dilates normal airway precontracted with methacholine. The fact that this effect is diminished or absent in asthma could be explained by the presence of bronchial inflammation. The hypothesis tested was that DI induces more relaxation in methacholine induced bronchoconstriction-solely determined by the smooth muscle contraction-than in exercise induced bronchoconstriction, which is contributed to by both smooth muscle contraction and airway wall inflammation.

Detailed Description
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Children were referred to the lung function department by their pediatric pulmonologist. Asthma was defined by a complaint of wheezing, cough, dyspnoea or chest tightness at rest or on exercising and a positive response to methacholine or exercise challenge. The response to exercise was considered positive when Forced Expiratory Volume in 1 s (FEV1) decreased at least 8% from Baseline. The response to methacholine was considered positive when FEV1 decreased at least 20% or Rrs increased at least 50% from baseline, at or below a cumulated dose of 1,200 μg. Bronchodilator medications were discontinued at least 12 hours prior to the testing and provocation allowed when the child had been free of respiratory symptoms for at least 2 weeks and baseline FEV1 was larger than 70% pred. Exercise and methacholine groups were matched for age, height, baseline FEV1 z-score, a moderate level of airway response to challenge and DI amplitude ranging 40-60% of the predicted Forced Vital Capacity (FVC). Written informed consent was obtained from the children and their parents for the procedures. Procedures for spirometry, exhaled fraction of NO (FENO), GrsDI (Respiratory conductance response to a deep inhalation) and challenges have been described previously. Acceptable GrsDI's were analyzed at a 10-20% FEV1 decrease from baseline. Statistics were performed using Mann-Whitney, Chi square tests and multiple regression as required. Data are median and interquartile range.

Official Title
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More Relaxation by Deep Breath on Methacholine- Than on Exercise-Induced Bronchoconstriction During the Routine Testing of Asthmatic Children

Conditions
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Childhood Asthma

Intervention / Treatment
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* Diagnostic Test: bronchial provocation test


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Children referred to the lung function department by their pediatric pulmonologist. Asthma defined by a complaint of wheezing, cough and dyspnoea. Positive response to methacholine or exercise challenge. Bronchodilator medications discontinued at least 12 h prior to the testing Provocation allowed when the child had been free of respiratory symptoms for at least 2 weeks and baseline FEV1 larger than 70% pred. Exclusion Criteria: - Other respiratory diseases than asthma

Ages Eligible for Study
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Minimum Age: 6 Years
Maximum Age: 14 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| test with methacholine<br> | Diagnostic Test: bronchial provocation test<br> <br> |
| test with exercise<br> | Diagnostic Test: bronchial provocation test<br> <br> |

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Grs change between before deep breath and after deep breath in exercise and metacholine groups | GrsDI represents Grs measured after deep breath reported to Grs before deep breath (bronchial provocation test) | through study completion, an average of 1 hour | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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airway smooth muscle, asthma, bronchial test, lung function