In 4343 spirometric tests performed before and after administration of a bronchodilator drug in Dijkzigt Academic Hospital (Rotterdam) the relationship between the initial value of FEV1 and IVC (expressed as Z-score = standard deviation score, SDS) and the response (the change expressed as a percentage of the predicted value) was as shown in the figures. By and large the response is smaller when the FEV1 and IVC are only mildly or moderately diminished with respect to the predicted value.