Assessment and prevention of exercise-induced bronchoconstriction

Abstract

The assessment of exercise-induced bronchoconstriction (EIB) in athletes requires the measurement of forced expiratory volume in 1 s (FEV(1)) before and after vigorous exercise or a surrogate of exercise such as eucapnic voluntary hyperpnoea (EVH) of dry air or mannitol dry powder. Exercise testing in a laboratory has a low sensitivity to identify EIB, and exercise testing in the field can be a challenge in itself particularly in cold weather athletes. The EVH test requires the subject to ventilate dry air containing ∼5% CO(2) for 6 min through a low-resistance circuit at a rate higher than that usually achieved on maximum exercise. A ≥10% reduction in FEV(1) is a positive response to exercise and EVH and, when sustained, is usually associated with release of inflammatory mediators of broncho constriction. Another surrogate, mannitol dry powder, given by inhalation in progressively increasing doses, is used to mimic the dehydrating stimulus of exercise hyperpnoea. A positive mannitol test is a 15% fall in FEV(1) at ≤635 mg and reveals potential for EIB. Mannitol has a high specificity for identifying a clinical diagnosis of asthma. Once a diagnosis of EIB is established, the athlete needs to know how to avoid EIB. Being treated daily with an inhaled corticosteroid to reduce airway inflammation, inhaling a β(2) agonist or a cromone immediately before exercise, or taking a leukotriene antagonist several hours before exercise, all inhibit or prevent EIB. Other strategies include warming up prior to exercise and reducing respiratory water and heat loss by using face masks or nasal breathing.

Reproducibility of the bronchoconstrictive response to eucapnic voluntary hyperpnoea

“…[10][11][12][13][14] Instead, EIB diagnosis should be objective and based on a fall in forced expiratory volume in 1 s (FEV 1 ) after an exercise challenge, or a surrogate for exercise such as eucapnic voluntary hyperpnoea (EVH). 7,9 Exercise challenges are highly specific, but they lack sensitivity and thus the rate of false-negative diagnoses can be high. 13,15 Exercise challenges are also difficult to standardise due to changing environmental conditions and ventilatory responses, which determine the degree of EIB.…”

Exercice-induced bronchoconstriction among athletes: Assessment of bronchial provocation tests

“…41 However, environmental conditions, such as humidity and temperature levels, pollen count and pollution level may greatly affect the response to the field. 42 A limitation of our study is that all the BPTs were not performed by all subjects. A further important limitation of our study is that almost half of athletes from Group A were under treatment with ICS and the relatively short ICS washout period (<3 days) may have led to some false-negative test results.…”

Exhaled Breath Temperature in Asthmatics and Controls after Eucapnic Voluntary Hyperventilation and a Methacholine Challenge Test

“…The prevalence of positive methacholine challenge tests in the general population has been reported to range from <10% to >40% in various studies, and normal variations in BHR can be expected even among subjects selected for the absence of known potential causes of a positive challenge test, such as asthma [31]. Similar variations are most probable even for indirect tests of BHR, even though they normally display a higher specificity [32]. …”