The iron lung machine, a 20th-century invention, served as a life-saving medical device for individuals unable to breathe independently. This mechanical respirator offered respiratory support when few alternatives existed for patients with compromised breathing. It sustained life for those whose respiratory muscles had failed, allowing for recovery or long-term survival.
The Mechanics of the Iron Lung
The iron lung operates as a negative pressure ventilator, mimicking natural breathing. The patient’s entire body, except for their head, is enclosed within a large, airtight cylindrical chamber. A tight rubber seal around the neck ensures the space remains sealed from outside air.
Inside the sealed chamber, a pump system, often using bellows or a diaphragm, continuously varies the air pressure. For inhalation, air is actively pumped out, creating a slight vacuum or negative pressure. This reduction in external pressure causes the patient’s chest and abdomen to expand, drawing fresh air into their lungs through their exposed nose and mouth.
After inhalation, air inside the cylinder is compressed slightly or allowed to equalize to ambient room pressure. This increase in external pressure causes the patient’s chest and abdomen to partially collapse, passively forcing air out as they exhale. This rhythmic cycling of negative and positive pressure effectively simulates chest cavity expansion and contraction, enabling breathing.
Why Iron Lungs Were Used
Iron lungs primarily provided respiratory support for patients with paralyzed or severely weakened breathing muscles. The most prominent condition was poliomyelitis, or polio. Polio is a viral disease attacking motor neurons, leading to muscle paralysis, including respiratory muscles.
During mid-20th century polio epidemics, especially peaking in the U.S. around 1952, many patients experienced respiratory failure. For those with affected diaphragm and chest muscles, the iron lung sustained breathing. While polio was the most common reason, iron lungs also treated other conditions causing respiratory muscle weakness, such as botulism or certain poisonings.
Modern Respiratory Alternatives
The widespread use of the iron lung declined due to advancements in public health and medical technology. A turning point was the development of effective polio vaccines by Jonas Salk and Albert Sabin in the 1950s and 1960s. Mass vaccination campaigns dramatically reduced polio incidence, leading to a 99 percent decrease in cases worldwide since 1988, making the iron lung largely obsolete for its primary purpose.
Modern respiratory support predominantly uses positive pressure ventilators. Unlike iron lungs, which create negative pressure around the body, these devices deliver air directly into the patient’s lungs, often via a tube (intubation) or mask. This method offers advantages like greater portability, less invasiveness, and improved patient access for medical care. Modern ventilators are now the standard for respiratory support in intensive care units and emergency settings.