[Critical analysis of the diagnostic value of the flow-volume curve]

Changes in the flow-volume curve after administration of a bronchodilator were studied in reversible bronchial obstruction. The concept of isovolume is used in analysis of the curve indices, i.e. it is felt that the index (75, 60, 50, 25% FVC) after administration should be fixed on the curve at the same volume as on the basic curve to enable an indirect account to be taken of changes in flow in function of time, since, if resistance is reduced, the emitted volume varies in the same period even though the conditions promoting the flow are unchanged.