Influence of forced inflations on static pressure-volume curve of the lungs and thorax in the dog.

Abstract

A study was made of the variations, under the influence of forced inspirations, of the static pressure-volume curve of lungs and thorax in dogs and of the dependence on time of these variations. The initial inflation curve, determined after a period of artificial ventilation, differs in shape from the second and following adapted curves. A progressive transformation of the pattern of the inflation curve is observed when the inflationary pressure is increased. Simultaneously, a displacement of the respiratory level occurs. Both phenomena are limited : the changes are observed only between critical lower and upper pressure values. To some degree, the variations in pattern of the inflation curve are also time-dependent. A second inflation at the same pressure produces a further adaptation but, following the second series of inflations, no further deformation can be achieved by repeating the inflations.In the interpretation of these variations, Berstein's hypothesis of the recruitment of previously closed alveoli, to explain the change in pattern of the pressure-volume curve, must be supplemented by some other mechanism producing the observed dependence on time of the observed processes.