Airway hyperresponsiveness and airway inflammation in elite swimmers

The prevalence of respiratory symptoms and airway hyperresponsiveness (AHR) is high in elite athletes; swimmers have one of the highest prevalences. No consensus exists on what airway challenge to use when identifying AHR in elite athletes. Further, knowledge is sparse about when during their active sport career AHR develops and if there is an acute effect on the airway inflammation of a swimming training session. We aimed to (i) evaluate the airway response to a methacholine challenge, a eucapnic voluntary hyperpnoea (EVH) test, a field-based exercise test (FBT) and a laboratory-based exercise test (LBT) in adult elite swimmers; (ii) investigate airway responsiveness and airway inflammation in adolescent elite swimmers; and (iii) evaluate the acute effect of a training session in an indoor swimming pool on airway inflammation in adolescent elite swimmers. Two groups were studied. (i) In adult elite swimmers (n = 16), we examined airway response in four airway provocation tests: methacholine challenge, EVH test, FBT and LBT. (ii) In adolescent elite swimmers (n = 33), we examined airway responsiveness to EVH and methacholine, and airway inflammation and compared the findings with those in asthmatic adolescents (n = 32) and unselected adolescents (n = 35). Further, we examined the acute effect of swimming on airway inflammation in a subpopulation of the adolescent swimmers (n = 21). Airway inflammation was evaluated using sputum induction, measurements of exhaled nitric oxide (FeNO) and exhaled breath condensate (EBC). Of 16 adult swimmers, eight (50%) had AHR; five of the eight (63%) were identified with the EVH test, four (50%) with the FBT, four (50%) with the LBT and none with the methacholine challenge [provocative dose of methacholine causing a 20% fall in FEV1 (PD(20)) <= 2 mu mol]. There were no differences in the prevalence of AHR to either EVH or methacholine (PD(20) <= 8 mu mol) among the adolescent swimmers, the asthmatic adolescents and the unselected adolescents. When looking at airway responsiveness as a continuous variable, the swimmers were more responsive to EVH than were the unselected subjects, and less responsive to methacholine than were the asthmatic adolescents. There were no differences in FeNO, EBC pH or in the cellular composition of the sputum among the three groups. Lung function, FeNO, EBC pH, EBC lactate and differential cell counts in sputum were not acutely affected by the swimming session. We found that the EVH test is the most sensitive test for identifying AHR in elite athletes when using the diagnostic criteria set forward by the International Olympic Committe. Whereas a high prevalence of AHR in adult swimmers was found, the prevalence of AHR in the adolescent swimmers did not differ from that in unselected adolescents nor did the adolescent swimmers have signs of airway inflammation. There was no acute effect of a swimming training session in an indoor chlorinated pool on lung function or airway composition in adolescent swimmers. We believe that elite swimming results in airway changes with AHR and airway inflammation.