A new simple spirometric index for use with bronchial provocation tests.

Spirometric indices such as the forced expiratory volume in one second (FEV1), the maximal expiratory flow rate (MEFR) and the maximal midexpiratory flow rate (MMFR) can be criticized for use with bronchial provocation tests since they are either partly effort-dependent or dependent on the forced vital capacity (FVC). These criticisms can be avoided by the use of a new index corresponding to the volume of air expired in one second starting at 75% of the control FVC, called the (FEV1)-25. This study was performed to evaluate the relative sensitivity of the (FEV1)-25 and the classical FEV1 in detecting airway obstruction caused by an inhaled carbachol aerosol in 20 asthmatic subjects. The mean fall in (FEV1)-25 of 46% following carbachol inhalation compared with a mean fall in FEV1 of 35% indicates that, in addition to its theoretical advantages, the (FEV1)-25 is a sensitive index for use with bronchial provocation tests.