The iron lung is a historical medical device that supported breathing for individuals unable to do so on their own. It represents an early form of mechanical ventilation, specifically a negative pressure ventilator. This technology assisted patients with respiratory muscle weakness.
How the Iron Lung Functions
The iron lung operates by creating changes in air pressure around the patient’s body to simulate natural breathing. A patient lies inside a large, airtight metal cylinder, with their head remaining outside through a sealed opening. Inside the chamber, a pump or bellows mechanism periodically decreases the air pressure, creating a slight vacuum. This negative pressure causes the chest cavity to expand, drawing air into the lungs, similar to how the diaphragm and intercostal muscles work during normal inhalation.
Following inhalation, the pressure inside the cylinder equalizes with the outside air, or becomes slightly positive, allowing the chest to naturally contract and air to be exhaled. This rhythmic cycling of pressure enables air to move in and out of the patient’s lungs.
Its Primary Medical Application
The iron lung found its primary medical application in treating conditions that caused respiratory paralysis. It was notably used for patients suffering from severe cases of poliomyelitis, commonly known as polio. Polio is a viral infection that can damage the motor neurons of the spinal cord, leading to muscle weakness or paralysis, including the diaphragm.
When polio affected these muscles, patients could no longer breathe effectively on their own, making the iron lung a life-sustaining intervention. The iron lung was also used for other conditions causing respiratory muscle weakness, such as botulism or certain types of nerve damage. For many patients, the iron lung provided temporary support until they recovered the ability to breathe independently, while others relied on it for extended periods.
The Iron Lung’s Place in History
The iron lung became a prominent medical symbol during the polio epidemics of the mid-20th century. Its invention by Philip Drinker and Louis Agassiz Shaw in 1928, with improvements by John Haven Emerson in 1931, provided a means of survival for thousands affected by respiratory paralysis. Hospital wards during the 1940s and 1950s often featured rows of these large machines, demonstrating their widespread use in managing the acute phase of polio.
The widespread availability of polio vaccines, starting in the mid-1950s, dramatically reduced the incidence of the disease, leading to a significant decline in the need for iron lungs. The development of more portable and less invasive positive pressure ventilators, which push air directly into the lungs, offered a different approach to mechanical ventilation. These advancements rendered the iron lung largely obsolete in modern medicine. Although rare, a few individuals continue to use iron lungs today, relying on these machines for their long-term respiratory support.