Diagnosis of Exercise-induced Bronchoconstriction in Swimmers: Context Matters.

Swimmers have a high prevalence of exercise induced bronchoconstriction (EIB), which may be associated with repeated exposure to chlorinated pool water. The eucapnic voluntary hyperpnea (EVH) test is used to diagnose EIB; however, it fails to replicate the environmental conditions experienced by swimmers. The relationship between the composition of the EVH inspired gas and the development of EIB from swim exercise remains unclear. PURPOSE: To compare the bronchoconstrictive effect of a chlorinated inspirate EVH test and swim test to laboratory-based EVH test in swimmers. METHODS: 15 collegiate swimmers (n=5 male, n=10 female; 21+/-2 years) completed three days of testing in pseudorandom order; a standard EVH test (EVHL), a pool air EVH test (EVHCl), and a swimming test (Swim). Spirometry was measured at baseline, and 3-, 5-, 10-, 15-, and 20-minutes following each test. RESULTS: EVHL elicited a forced expired volume in one second (FEV1) fall index of -9.7+/-6.4 % compared to -6.6+/-9.2 % and -3.0+/-7.5 % following EVHCl and Swim, respectively (p<0.05). Using Bland-Altman analysis we found good agreement between EVHL vs EVHCl (bias= -2.8, r= 0.79) (p<0.05) with poor agreement between EVHL vs. Swim (bias = -6.7, r= 0.20) and EVHCl vs Swim (bias = -3.9, r= 0.50) (both p<0.05). Forced expired flow between 25 and 75 % lung volume (FEF25-75) and peak expired flow (PEF) were significantly reduced by the EVHL compared to the EVHCl and Swim tests (p<0.05). CONCLUSION: EVHL elicits a greater FEV1 fall index than EVHCl and Swim. The unique aquatic environment of swimmers potentially protects against bronchoconstriction and should be considered in the determination of EIB.