Effects of maximal breath holding on maximal expiratory flows

Effects of breath holdings (BH) on bronchomotor tone, maintained until their breaking points, have been studied using maximal expiratory flow volume curves (MEFVC). BHs have been performed either at high lung volume (total lung capacity, EIBH) or at low lung volume (residual volume +250 ml, EEBH), an inspiratory manoeuvre immediately preceding the MEFVC. The results show that: (1) EIBH induces a significant increase of expiratory flow at 25% of FVC; (2) EEBH induces a significant and constant decrease of expiratory flows at 50% and 25% of FVC. The same modifications were recorded after inhalation of 400 micrograms of Fenoterol or 80 micrograms of Ipratropium bromide. The observed results are suggestive of mechanical effects of BH on expiratory flows. After EIBH airway hysteresis dominates over lung hysteresis, with opposite effects after EEBH.