Iron Lung

A negative-pressure mechanical ventilator that encloses the body from the neck down, cyclically lowering air pressure inside its rigid chamber to expand the chest and draw air into the lungs, then raising it to allow exhalation, for a patient whose own breathing muscles are too weak or paralyzed to work unaided. Developed in the late 1920s by Philip Drinker and Louis Agassiz Shaw at Harvard, the device became the dominant treatment for the respiratory paralysis caused by poliomyelitis through the middle of the twentieth century, filling hospital wards known as polio wards with rows of patients breathing entirely through the machines for weeks, months, or in some cases years. Because it works by moving the whole chest wall rather than pushing air directly into the airway, it avoids many of the complications of a tube inserted into the throat, though it also confines the patient almost completely and makes nursing care difficult. Its use declined sharply after the introduction of positive-pressure ventilators, which deliver air through a mask or tube instead of surrounding the body, and after polio vaccination reduced the disease that had made the device so widespread, though a small number of long-term polio survivors continued to depend on their machines decades later.