- Related Topics:
- therapeutics
- polio
- lung
- breathing
- paralytic polio
- On the Web:
- Science Museum - The Iron Lung (Oct. 22, 2026)
iron lung
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What is an iron lung?
An iron lung is a large mechanical medical device that helps people breathe when they can't on their own. It's essentially a mechanical respirator inside a horizontal metal cylinder. A bellows moves in and out, changing the pressure and stimulating breathing.
The first iron lung, known as the Drinker respirator, was invented in 1927 by Philip Drinker and Louis Agassiz Shaw. The patient lies on their back inside the airtight chamber with their head and neck outside. The device pulls air out, creating negative pressure to draw fresh air in, mimicking the diaphragm's action. Then, it reverses, creating positive pressure to push air out.
Historically, iron lungs were often used to treat polio patients. Use of iron lungs declined after the introduction of the polio vaccine in the 1950s and is now generally considered obsolete.
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Why was the iron lung invented?
The iron lung was invented to help people breathe, especially those who had been affected by paralysis caused by polio. Polio epidemics became more common in industrialized countries in the late 19th and early 20th centuries. The first iron lung was invented in 1927 by Philip Drinker and Louis Agassiz Shaw, and it was first used on patients in 1929. The device works by changing the pressure inside a chamber, which helps to stimulate breathing. As the diaphragm of the iron lung moves, it pulls air out of the chamber, creating negative pressure that allows fresh air to be drawn in. Use of the iron lung declined after the introduction of the polio vaccine in the 1950s.
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How does an iron lung help people breathe?
An iron lung is a medical device that helps people breathe when they can't on their own. The device consists of a horizontal metal cylinder that encloses most of a person's body. With the patient lying on their back with their head and neck outside of the chamber, a bellows positioned at the foot end of the machine moves in and out to change the pressure within the chamber, which stimulates breathing.
The movement of the iron lung's diaphragm is the primary mechanism by which the machine aids respiration. When the diaphragm moves in one direction, it pulls air out of the chamber, creating negative pressure that allows fresh air to be drawn in. When the diaphragm moves in the opposite direction, it produces positive pressure, which causes the patient's lungs to contract and push air out.
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What kind of illnesses made people need an iron lung?
Historically, iron lungs were primarily used to aid patients with paralysis caused by polio, specifically paralytic polio, who were unable to breathe on their own. The poliovirus would attack cells in the spinal cord and brainstem, potentially leading to difficulties in breathing.
The iron lung helped patients breathe by creating pressure changes that mimicked the action of the diaphragm, pulling air in and out of the lungs. Although primarily associated with polio, the iron lung was also used to treat individuals with coal gas poisoning and similar conditions that impaired breathing. Use of iron lungs declined after the polio vaccine was introduced in the 1950s.
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How does the iron lung work differently from modern ventilators?
The iron lung and modern ventilators work differently to facilitate breathing. The iron lung, a large metal cylinder enclosing most of the body, employs negative pressure to mimic natural breathing. A bellows creates a vacuum around the chest, expanding the lungs and drawing air in. Releasing the vacuum allows the chest to recoil, pushing air out.
Modern ventilators use positive pressure to push air into the lungs. Once the breath ceases, airway pressure drops, and the chest walls automatically recoil, pushing the breath out through passive exhalation. The movement of the iron lung's diaphragm pulls air out of the chamber, creating negative pressure and allowing fresh air to be drawn in, similar to how the human diaphragm functions.
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Why are iron lungs rarely used today?
Today, iron lungs are rarely used because polio vaccines have nearly eradicated the disease that caused the paralysis requiring their use. Additionally, advancements in mechanical aids, like positive pressure ventilators that pump air directly into the lungs through a tube in the windpipe, have provided a more effective and less restrictive alternative.
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iron lung, mechanical medical device, sufficiently large to enclose most of an individualās body, used to maintain respiration in persons who are unable to breathe on their own. An iron lung, the main portion of which consists of a horizontal metal cylinder, essentially acts as a mechanical respirator, wherein a bellows positioned at the foot end of the machine moves in and out to produce changes in pressure that stimulate breathing.
Historically, the iron lung was used for patients affected by paralysis caused by polio; many such patients were unable to breathe on their own. After the early 1950s, following the introduction of the polio vaccine, use of the iron lung declined, such that today it is generally considered obsolete.
History
The first iron lung was invented in 1927 by Philip Drinker and Louis Agassiz Shaw at Harvard University; it was implemented with patients in 1929. The machine, known as the Drinker respirator, consisted of an airtight chamber that enclosed the body, with bellows attached at the foot end and a rubber seal at the opposite end to prevent air leakage around the patientās neck. The Drinker respirator was used to treat patients with paralytic polio and individuals who were unable to breathe as a result of coal gas poisoning and similar conditions. In 1931 another version of the machine, which included features such as a leather bellows to help silence the machine and portholes through which doctors could access the patient for medical procedures, was invented by John Haven Emerson. The so-called Emerson respirator became increasingly common in hospitals and other medical facilities beginning in the late 1930s. In 1961, Mildred Stahlman and colleagues at Vanderbilt University Hospital used a modified iron lung to help save the life of a premature infant with underdeveloped lungs. This innovation helped to introduce a new era in neonatal care and establish the modern neonatal intensive care unit (NICU).
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How it works
In the iron lung, the patient lies on their back with the body inside the chamber and the head and neck resting on a stand outside the chamber. The movement of the diaphragm of the iron lung is the primary mechanism by which the machine aids respiration. Its movement one direction pulls air out of the chamber, producing negative pressure and allowing fresh air to be drawn in. This mechanism is similar to the way in which contraction of the diaphragm muscle in the human body lowers internal pressure in the lungs, thus expanding the thoracic cavity and causing inspiration of air. As the diaphragm of the iron lung then moves in the opposite direction, mimicking relaxation of the human diaphragm muscle, positive pressure is produced, causing the patientās lungs to contract and push air out.
Use of the iron lung typically was limited to a few weeks or months, depending on the severity of the patientās condition. For many patients, the iron lung was used alongside physical therapy, and some patients used the machine only at night or for only a few hours of the day. In a few instances, however, patients spent their entire lives in an iron lung. One such person was Paul Alexander, who lived in an iron lung after developing paralytic polio in 1952, when he was six years old. Alexander was unable to leave the chamber for more than a short period of time every day. Nonetheless, he attended law school and started his own law practice; he died in 2024.