[Measurement of the effect of a bronchodilator using FEV1: how to express it?].

An assessment of the effect of a bronchodilator on VEMS (FEV1) is based on a "before and after" comparison with the chosen drug. Most often the percentage rise in FEV1 compared to the initial value is calculated (I), and a minimum of 20% reversibility is expected for asthma. But the change of FEV1 expressed as a percentage of predicted theoretical value (II) may also be calculated. With the help of 50 cases of asthma selected by the first criteria (I) after an inhalation of an adrenergic stimulant the following changes were shown: That the first method (I) is biased, over estimating for low initial values; That the second method (II) was not inconvenient and furnished all the information derived. It shows in particular that 14/50 subjects have a variation of FEV1 less than 10% of their theoretical value, which has considerable therapeutic interest and merits further discussion.