What is the diagnostic test for exercise-induced bronchospasm that shows a 10% reduction in FEV1?

Eucapnic voluntary hyperventilation is a diagnostic test specifically used to assess exercise-induced bronchospasm (EIB). In this test, the patient breathes a gas mixture with a controlled level of carbon dioxide while undergoing hyperventilation. This mimics the physiological conditions experienced during exercise and can provoke bronchoconstriction in susceptible individuals. A reduction of at least 10% in forced expiratory volume in one second (FEV1) from baseline indicates the presence of bronchospasm, confirming the diagnosis of EIB.

This method is particularly effective since it allows for controlled respiratory conditions that can trigger bronchoconstriction similar to those during physical activity, thereby providing relevant diagnostic information about the patient's airway responsiveness.

The other options, while they may also assess airway reactivity, do not provide the same direct evidence of bronchial hyperreactivity in the context of exercise challenge as eucapnic voluntary hyperventilation does.