PubMed · 1759313
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M A Ben Mustapha, K Ben Hassine. [Exercise-induced asthma].. https://pubmed.ncbi.nlm.nih.gov/1759313/
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Cough and wheezing interferes with sport and other forms of physical activity in half of asthmatic children. Airway obstruction can be induced by a standard exercise test in over 70% of children with asthma. A beta-adrenergic agonist or cromone taken by inhalation beforehand will usually inhibit bronchoconstriction provoked by a free running exercise test. The duration of protective effect with salbutamol, terbutaline and cromones is less than 4 h. The long acting beta-adrenergic agonists formoterol and salmeterol give protection against exercise-induced airway obstruction for up to 12 h, which implies that treatment given in the morning will offer protection from the effects of physical activity throughout the day. However, the duration of protective effect after a morning dose declines if these compounds are given regularly. Leukotriene receptor antagonists (LRAs) also provide good protection against exercise-induced asthma. Regular administration of LRAs is not associated with tolerance and loss of protective effect. The oral route makes for unobtrusive administration and this may help adherence to prescribed regimens.
OBJECTIVE: Exercise-induced bronchoconstriction (EIB) may be demonstrated in 60-70% of asthmatic children in temperate climates. In areas of high humidity it is postulated to be low. The aim of the study was to determine the prevalence of EIB in a population of schoolchildren with wheezing, living in the humid tropical climate of Kuala Lumpur, Malaysia. METHOD: We performed a cross-sectional study using the International Study of Asthma and Allergies in Childhood questionnaire to identify 7-12-year-old Malay children with asthma symptoms from a primary school in central Kuala Lumpur. Sixty-five of 76 children with 'ever wheeze' performed an exercise challenge test successfully in an uncontrolled environment. A random sample of 80 schoolchildren with no history of wheeze were similarly tested as controls. The relative humidity and temperature were recorded. A fall of > 15% was considered as clinically important. RESULTS: The prevalence of EIB in schoolchildren with 'ever wheeze' was 47.7%. The prevalence of EIB in children with 'current wheeze' was 51.6%. The prevalence of EIB in controls was 7.5%. The relative humidity during the study ranged from 41 to 90%. There was no significant relationship between different humidity levels and EIB (P = 0.58, regression analysis). CONCLUSION: This study demonstrates that EIB is present in asthmatic children despite the highly humid tropical environment.
Exercise-induced asthma, as recognized in asthmatic subjects, is an exaggerated airway response to airway dehydration in the presence of inflammatory cells and their mediators. The airway narrowing is primarily caused by contraction of bronchial smooth muscle. The milder airway narrowing documented in response to exercise in elite athletes and otherwise healthy subjects may simply be the result of the physiologic responses and pathologic changes in airway cells arising from dehydration injury. These changes, which include excessive mucus production and airway edema, would serve both to cause cough and to amplify the narrowing effects of normal bronchial smooth muscle contraction, resulting in symptoms. These changes are more likely to occur in healthy subjects who exercise intensely for long periods of time breathing cold air, dry air, or both. Under these conditions, the ability to humidify inspired air may be overwhelmed, causing significant dehydration of the airway mucosa and an increase in osmolarity, even in small airways. In addition to dehydration injury, airway narrowing to pharmacologic and physical agents may occur as a result of injury caused by large volumes of air containing irritant gases, particulate matter, or allergens being inspired during exercise. As a result, the airways may become inflamed, and the airway smooth muscle may become more sensitive. These events could result in the same exaggerated airway response to dehydration, as documented in asthmatic subjects.