Lung Elastic Recoil in Cystic Fibrosis1,2

The pressure-volume behavior of the lung was studied in 24 patients with cystic fibrosis. Isovolume flow-pressure relationships were measured in 7 of these patients, and a modification of the flow-volume test was evaluated for detection of flow reduction in a separate group of 63 patients. Relative to results in a control group of 31 normal subjects, 13 of the 24 patients had grossly abnormal pressure-volume curves with excessive stiffness of the lung near maximum volume and loss of recoil at lower volume. Closing volumes in these patients were often high enough to cause significant disturbances in gas exchange and the elevated closing volumes were quantitatively explained by the low values for elastic recoil. The modified flow-volume test detected mild flow reduction in many patients who otherwise had normal pulmonary function tests. Loss of recoil per se did not account for the low maximum expiratory flows, since “upstream” resistances were high. However, pressure-flow curves were effort-dependent at hi...