Alternatives to exercise challenge for the objective assessment of exercise-induced bronchospasm: eucapnic voluntary hyperpnoea and the osmotic challenge tests

Educational aims

1. To describe alternative tests for the assessment of exercise-induced bronchoconstriction and to describe the mechanisms by which bronchoconstriction is caused.

2. To describe how these tests are performed and how to interpret the test results.

3. To choose the most appropriate test for a given clinical problem.

Summary Exercise-induced bronchoconstriction (EIB) is caused by evaporative water loss due to conditioning large volumes of air in a short period. This leads to an increase in osmolarity of the airway surface, which provides a favourable environment for release of bronchoconstricting mediators from inflammatory cells in the airways. Thus, stimuli that mimic this water loss or increase the osmolarity of the airway surface may be used as ‘surrogates’ for exercise challenge testing. The most widely used tests are eucapnic voluntary hyperpnoea (EVH) or osmotic challenges (e.g. hyperosmolar saline and mannitol). However, there are some differences in the methodology that need to be considered when using these tests. Importantly, EVH and the osmotic challenge tests overcome some of the practical and safety limitations of performing exercise testing at high intensity. The utility of these alternative tests for assessing EIB is discussed.