[Comparison between the closing volume comportments and the Vmax/V curve in patients with obstruction of the small airways].

Three groups of patients with obstruction of the small airways and normal main airways were submitted to study by determining the closing volume and the V max/V curve. In the first group (beginning chronic bronchitis) was noted an alteration of the curve with normal closing volume in almost all the cases; in the second group (asthma in the remission phase) the closing volume was increased and the curve normal in a part of the patients, -while in the other part the closing volume was normal and the curve altered; in the third group (recent heart infarct), a significative increase in the closing volume was noted with a slightly altered curve: improvement of the tests was obtained after administration of diuretics, the improvement being far more noticeable for the closing volume than for the V max/V curve. The closing volume is therefore an extremely sensitive test of the obstruction of the small airways when the obstruction interests before all the basal zones of the lungs. When the resistances of the small airways are irregularly distributed, the determination of the V max/V curve is, conversely, more useful.