[Interest of helium-oxygen flow volume and isoflow volume curves in chronic obstructive lung disease (author's...

We have compared changes in maximal flows induced by breathing gases of different density in 54 patients suffering from emphysema and chronic bronchitis. We considered as positive responders those subjects displaying an increase by at least 20% of maximal expiratory flows while breathing gases of lower density. Such a response was demonstrated in 21 cases, the remainder (33 cases) being non-responders. Hence, in such patients, airways obstruction may primarily be localised in central or peripheral airways. There was no correlation between the nature of this response and the clinical diagnosis, but non-responders, in general, were those in whom respiratory insufficiency was more severe. There seemed to be no additional information gained by measuring isoflow-volume (iso V vol.) in comparison with measuring differences in maximal flows at 50% of vital capacity.