Surface Properties in Relation to Atelectasis and Hyaline Membrane Disease

Recent observations suggest that a low surface tension may be an important attribute of the lining of the air passages of the lung.^1-4The purpose of this paper is to present evidence that the material responsible for such a low surface tension is absent in the lungs of infants under 1,100-1,200 gm. and in those dying with hyaline membrane disease. The role of this deficiency in the pathogenesis of the disease is considered. Surface tension operates so as to minimize the area of the surface. In the lungs, where the internal surface (the alveolar lining) is curved concave to the airway, the tendency of the surface to become smaller promotes collapse. Although the forces not only of surface tension but also of the elastic tissue tend to collapse the lungs, their behavior differs in one important respect. When the lung contains only a small volume of air, the elastic