Evaluation of Exercise Induced Bronchoconstriction by Field Test Using Lung Function and a Novel Automated Digital Clinical Decision System

Asthma is the most common chronic condition in Olympic athletes. Asthma is defined as a chronic inflammation in the airways associated with bronchial hyper responsiveness (BHR). It is suggested that there are two phenotypes of asthma among athletes; the classic asthma with early childhood onset and allergic sensitization, and the "sports asthma". While exercise-induced "sports" asthma (EIA) describes symptoms and signs of asthma provoked by exercise, exercise-induced bronchoconstriction (EIB) is defined as the transient narrowing of the lower airway after exercise. In the general population, EIB with or without asthma affects 5% to 20%, but the rate is estimated to be even higher in top athletes participating in winter and summer endurance sports.

Asthma and EIB represent an important challenge for the athlete, and correct diagnosis is important as it affects health as well as performance with strict regulations concerning asthma medication. A clear diagnosis of asthma with confirmation of BHR is strongly suggested by the International Olympic Committee (IOC) and the World Anti-Doping Agency (WADA) before the use of anti-asthmatic medication.

Presence of BHR is demonstrated by direct or indirect bronchial provocation testing. Direct bronchial provocation causes bronchoconstriction by acting on specific airway receptors on the bronchial smooth muscle, while indirect bronchial provocation tests acts indirectly via the release of contractile mediators. Direct bronchial provocation via inhalation of methcacholine has been reported to be highly sensitive in detecting BHR in elite athletes, and is the method of choice at Olympiatoppen, Norway. To reduce the risk of false positive BHR results, methacholine provocation is only used in patients with symptoms of EIA. Less sensitive but more specific, is indirect bronchial provocation including several methods for the diagnosis of EIB. The most intuitive is exercise (field and laboratory) challenge testing (ECT), but sensitivity has been reported to be low, since exercise load and intensity have large impact on ability to detect EIB and in field-testing (FT), standardizing ambient conditions are impossible. By eucapnic voluntary hyperpnoea (EVH) of dry air, the two components of EIB are induced: The inflammatory cascade in the airways causing airway smooth muscle contraction, and airway oedema. The EVH has been endorsed by the IOC-MC as the gold standard due to its high specificity, but for mild to moderate EIB, EVH has wide sensitivity, specificity and poor repeatability, which may rely on inability to simulate the competition environment. Suboptimal tests for EIB may explain why previous papers report poor relationship between symptoms of EIA and the objective EIB in athletes, leaving the actual rate of EIB remains unclear. What has been argued to be the true "gold standard" is a sports-specific exercise FT , performed in the actual training conditions which also makes it easier for the athlete to perform at maximum exercise. The advantages of monitoring with peak expiratory flow (PEF) or forced expiratory volume in 1 s (FEV1) outside a laboratory with a PEF meter or spirometer, respectively, are that it is simple and cheap. It also enables measure of bronchial challenge testing in close relationship to symptoms, since laboratory bronchial challenge testing often are negative in subjects being away from their profession too long. Due to lack of standardization, it is recommended to measure serial lung function after a specific exercise in at least two different time-points. However, traditional non-digital method of serial PEF/FEV1 monitoring has limitations with poor adherence, interpretation difficulties with objectivity and time-consuming analysis and reading of paper PEF/FEV1 plots.

Recently, AsthmaTuner (Medituner AB) consisting of a patient smartphone application, a portable wireless spirometer for measuring lung function (PEF/FEV1), and a healthcare interface including treatment plan, was reported to significantly improve management of uncontrolled asthma. Such electronically clinical decision support systems (CDSS) has gained acceptance for the diagnosis of asthma, and by the ability to assess patient generated data in field ECTs, the CE-marked AsthmaTuner may provide athletes a feasible, time and cost-efficient self-monitoring of EIB and asthma. AsthmaTuner may also empower athletes in monitoring their lung function over time. These lung function measurements contain unexpected amounts of information for identifying athletes with distinct phenotypes of EIB due to strenuous sports and environmental conditions. Hence, AsthmaTuner have the potential to fill the knowledge gap regarding prevalence of EIB, development of EIB and the lack of association between symptoms and detection of EIB in athletes.

Objective and aims The primary objective of this study on elite athletes with symptoms of EIB, is to assess if EIB can be determined equally by repeated standardized and unstandardized field ECT using AsthmaTuner, and EVH.