Pathogenesis of exercise induced bronchoconstriction

Exercise induced hyperventilation leads to profound changes at the level of bronchial airways that in some subjects may prevent, but in others facilitate the development of exercise induced bronchoconstriction (EIB). Cooling and rewarming, water loss, cellular shrinkage and inflammation of the bronchial wait during exercise are all thought to predispose to EIB. The main pathogenetic theory on EIB is that exercise hyperventilation causes drying of the airways and increases fluid osmolarity of the airways surface that makes bronchial epithelial. cells "shrink" and release inflammatory mediators. On the other hand, the stretching of bronchial smooth muscles induced by the increase in tidal volume (V-T) should prevent the development of EIB, but in asthmatic patients stretching of respiratory smooth muscle induced by lung inflation does not decrease the bronchoconstrictor response to methacholine.