Diagnosis of exercise-induced bronchoconstriction: eucapnic voluntary hyperpnoea challenges identify previously undiagnosed elite athletes with exercise-induced bronchoconstriction
Dickinson J, McConnell, A, Whyte G. Br J Sports Med. 2011;45:1126-1131.
http://www.ncbi.nlm.nih.gov/pubmed/20647298
http://www.ncbi.nlm.nih.gov/pubmed/20647298
Exercise-induced bronchospasm (EIB) is an obstruction of transient airflow that usually occurs 5-15 minutes after exercise. Although the previously reported incidence of EIB has been around 20%, the authors of this manuscript believe that (EIB) may be more prevalent than clinicians think and should be screened for. The purpose of this study was to use a eucapnic voluntary hyperventilation (EVH) challenge as a surrogate for exercise to screen elite British athletes for EIB. The EVH challenge involved the athletes reaching a target minute ventilation of 85% of their predicted maximal voluntary ventilation rate for 6 minutes. Maximal flow volume loops were measured at baseline and 3, 5, 10 and 15 minutes following the EVH challenge. EIB was diagnosed as a fall in FEV1 by at least 10% from baseline at two consecutive time points. This EVH challenge had previously been shown by the same authors to have a high specificity and sensitivity in diagnosing EIB in elite athletes. Two hundred and twenty eight elite British athletes from a variety of different sports were screened. Following the EVH challenge, 78 (34%) of the subjects were diagnosed with EIB. Of those diagnosed with EIB, 57 (73%) did not have a previous diagnosis of EIB. Of those 30 athletes, 9 (30%) who reported a previous diagnosis of asthma had EVH testing that was negative for EIB. Of the athletes who tested positive for EIB with no previous diagnosis of asthma, 29 (50%) reported symptoms of EIB. The authors conclude that, given incidence of undiagnosed EIB in elite athletes, all elite athletes should undergo EIB screening with an EVH challenge.
There are compelling reasons to screen all athletes for EIB. The authors point out that the IOC-MC requires every request to use inhaled beta agonists be justified by evidence of bronchoconstriction through a bronchodilator or bronchoprovocation challenge to ensure that asthma medications are not used simply to try to gain a competitive edge. In addition, the risk of acute bronchoconstriction causing mortality in athletes with EIB should certainly be avoided, if possible. The feasibility of screening athletes with EVH in most sports medicine offices is much simpler than having an athlete exercise to the point of maximal lung capacity as it requires only the appropriate pulmonary testing equipment. This paper suggests that we can do it, the bigger question is; should we do it?. The prevalence of EIB in athletes is higher than the prevalence of asthma in the general population and, in certain sports, the prevalence approaches 39-44% of athletes, according to prior studies by these authors. These sports are considered to be more “asthmogenic” because they have a high ventiltatory requirement, but perhaps the “asthmogenic” nature of these sports is, in fact, physiologic. Maybe the high incidence of EIB in these athletes is simply picking up on what would normally happen if the lungs are worked hard enough. This situation may not be dissimilar to the athletic heart phenomenon when the heart is worked hard enough. Perhaps the lungs remodel in a way that only appears pathologic given the instruments we use to measure it. The question remains, would screening for, and treating the large percentage of asymptomatic athletes who were previously unaware of their EIB prevent mortality due to bronchoconstriction? Starting patients on beta agonists has not been shown to improve performance; however, these medications, and others, like inhaled corticosteroids, used to treat EIB are not without side effects and cost. Would you screen your athletes for EIB?
Written by: Hallie Labrador, MD and Marc I. Harwood, MD
Reviewed by: Kyle Harris
Related Post:
Dickinson J, McConnell A, & Whyte G (2011). Diagnosis of exercise-induced bronchoconstriction: eucapnic voluntary hyperpnoea challenges identify previously undiagnosed elite athletes with exercise-induced bronchoconstriction. British Journal of Sports Medicine, 45 (14), 1126-31 PMID: 20647298