Abstract
The physical properties of the lung were measured in 43 normal subjects, 18 patients with emphysema, 12 patients with allergic asthma, and 9 patients with diffuse pulmonary infiltration. There were obvious alterations in the elastic properties of the lung in the patients with emphysema that were not clearly shown by the compliance measurement. Data were presented that showed a clear distinction between patients with emphysema, asthma, and diffuse pulmonary infiltration when maximal inspiratory pressure was related to total lung capacity. This relationship was termed the "coefficient of retraction," because it was believed to convey better the concept of elastic recoil of the lung and hence its structural integrity.