Fig. 1

Indirect and direct bronchial provocation tests in asthma—mechanisms of action. Inhaled mannitol causes increased osmolarity of the periciliary liquid, which induces cell shrinkage as the water moves out of the cells to restore osmotic equilibrium. Through a calcium-dependent process, this leads to a release of bronchoconstricting mediators (e.g., histamine, prostaglandins and leukotrienes) from inflammatory cells, eventually causing smooth muscle contraction in responsive individuals. For further details, several reviews on the properties, safety and mode of action have been previously published [13, 14]. EVH: eucapnic voluntary hyperventilation test