[The arterio-alveolar CO2 gradient. Physiopathological and clinical significance]

The arterio-alveolar CO(2) gradient was examined in 20 patients with various ventilation diseases. It increased or became negative in obstruction. The tendency to increase was attributable to distribution disturbances, particularly the marked increase in the "dead space" effect. The same picture, though to a lesser degree, owing to a smaller dead space increase, was even more frequent in restriction cases. The appearance of a gradient in healthy subjects is referable to uneven air and blood distribution in the alveoli under physiological conditions. The physiopathological significance of negative gradients is discussed in the light of the results and the findings of other workers.