Disconnect between standardized field-based testing and mannitol challenge in Scottish elite swimmers

Background

Elite swimmers have high rates of rhinoconjunctivitis and exercise-induced bronchoconstriction. Moreover, exposure to chlorine and chlorine metabolites is known to induce bronchial hyper-reactivity.

Objective

To assess the early and late effects of chlorine and exercise on the unified airway of elite swimmers, and to compare the response to mannitol and field-based exercise challenge.

Methods

The Scottish national squad underwent exhaled tidal (FENO) and nasal (N-NO) nitric oxide measurement, peak nasal inspiratory flow (PNIF), and forced expiratory volume in 1 s before, immediately after, and 4-6 h post-swimming. A sport-specific exercise test was carried out during an intensive lactate set (8 min at >= 80% maximum hear rate). All swimmers underwent mannitol challenge, and completed a health questionnaire.

Results

N=61 swimmers were assessed: 8/59 (14%) of swimmers had a positive mannitol challenge. Nine out of 57 (16%) of swimmers had a positive exercise test. Only one swimmer was positive to both. Swimmers with a positive mannitol had a significantly higher baseline FENO (37.3 vs. 18.0 p.p.b., P=0.03) than those with a positive exercise challenge. A significant decrease in FENO was observed pre vs. immediate and delayed post-chlorine exposure: mean (95% CI) 18.7 (15.9-22.0) p.p.b. vs. 15.9 (13.3-19.1) p.p.b. (P < 0.01), and 13.9 (11.5-16.7) p.p.b. (P < 0.01), respectively. There were no significant differences in N-NO. Mean PNIF increased from 142.4 L/min (5.8) at baseline to 162.6 L/min (6.3) immediately post-exposure (P < 0.01). Delayed post-exposure PNIF was not significantly different from pre-exposure.

Conclusions

No association was found between mannitol and standardized field-based testing in elite swimmers. Mannitol was associated with a high baseline FENO; however, exercise/chlorine challenge was not. Thus, mannitol may identify swimmers with a 'traditional' inflammatory asthmatic phenotype, while field-based exercise/chorine challenge may identify a swimmer-specific bronchoconstrictor response. A sustained fall in FENO following chlorine exposure suggests that a non-cellular, perhaps neurogenic, response may be involved in this group of athletes.

Cite this as: K. L. Clearie, P. A. Williamson, S. Vaidyanathan, P. Short, A. Goudie, P. Burns, P. Hopkinson, K. Meldrum, L. Howaniec and B. J. Lipworth, Clinical & Experimental Allergy, 2010 (40) 731-737.