Iron lung. Raymond Nelson, age 2, and volunteer Ann Sanders. The Iron lung was first developed in the 1920's, and was often used in the treatment of polio victims. The respiratory muscles of persons stricken with polio are often paralyzed, quickly leading to death from anoxia. In the iron lung, electric bellows create alternate negative and positive pressures in an airtight metal tank. Negative pressure contracts the patient's diaphragm causing inhalation, and positive pressure expands the diaphragm to cause exhalation. Photographed at Rancho Los Amigos, Hondo, California.