The iron lung was a large, historical medical device that provided breathing support for individuals unable to breathe on their own. This mechanical respirator offered a means of survival for patients who had lost the ability to breathe due to various conditions.
How the Iron Lung Provided Breathing Support
The iron lung operated on the principle of negative pressure ventilation, mimicking the natural mechanics of breathing. A patient’s entire body, except for their head, was enclosed within a large, airtight metal tank. A tight rubber seal around the neck ensured the chamber remained sealed from the outside air.
Inside the sealed chamber, an electric motor-driven pump, often using bellows, would rhythmically decrease and increase the air pressure. When the pressure inside the tank dropped, it created a slight vacuum, causing the patient’s chest and abdomen to expand. This expansion drew air into the lungs through the patient’s nose and mouth, which were exposed to the outside atmosphere.
Conversely, when the pump allowed air back into the tank, the pressure inside would rise, causing the patient’s chest to naturally contract. This action passively pushed air out of the lungs, simulating exhalation. This rhythmic change in pressure allowed the patient to inhale and exhale, effectively breathing for them by moving their chest wall externally, unlike modern ventilators that push air directly into the lungs.
The Iron Lung and the Polio Epidemics
The iron lung found its most extensive use during the poliomyelitis, or polio, epidemics of the mid-20th century. Polio was a viral disease that could cause muscle paralysis, affecting respiratory muscles in severe cases and leading to an inability to breathe independently. Without assistance, patients whose breathing muscles were paralyzed faced death by suffocation.
During the peak of the polio epidemics, particularly in the United States in 1952 when nearly 58,000 cases were recorded, hospital wards often contained rows of these large metal respirators. The iron lung saved thousands of polio victims by providing essential mechanical support. While some patients required the iron lung for only weeks or months, those with permanent paralysis of their chest muscles were confined to the device for their entire lives.
Transition to Modern Respiratory Support
The widespread use of the iron lung began to decline with the advent of the polio vaccine. Jonas Salk’s polio vaccine, licensed in 1955, reduced the incidence of the disease. By 1957, the number of polio cases in the U.S. had decreased, and by the 1960s, paralytic polio affected fewer than 10 Americans annually.
Simultaneously, advancements in medical technology led to the development of modern positive pressure ventilators. These newer devices work by actively pushing air directly into a patient’s lungs, often through a tube inserted into the airway. Positive pressure ventilators are smaller, more portable, and allow for greater patient access and mobility compared to the bulky iron lung. While a few individuals with long-term respiratory paralysis from polio continued to use iron lungs, these newer, less invasive methods became the standard for respiratory support.