An iron lung is a type of mechanical respirator designed to assist breathing when an individual’s muscle control is compromised or the effort of breathing exceeds their capabilities. This device, a negative pressure ventilator, encloses most of a person’s body and manipulates air pressure within the sealed space to enable respiration. The iron lung held significant historical importance, particularly during the polio epidemics of the 20th century, serving as a life-saving medical invention. It offered a means of survival for patients unable to breathe independently.
How the Iron Lung Worked
The iron lung operated on negative pressure ventilation, mimicking natural breathing. A patient would lie inside a large, airtight cylindrical chamber, with their head remaining outside through a sealed opening at one end. An electric motor powered a mechanism, often a flexible diaphragm or bellows, to rhythmically change the air pressure inside the cylinder.
To initiate inhalation, air was actively pumped out of the chamber, creating a slight vacuum or negative pressure around the patient’s body. This pressure difference caused the chest and abdomen to expand, drawing air into the lungs through the patient’s nose and mouth. When the air inside the cylinder was then allowed to return to normal atmospheric pressure, or slightly compressed, the chest cavity would naturally contract. This passive contraction expelled air from the lungs, completing the exhalation phase.
This continuous cycling of pressure allowed the patient to breathe without muscular effort. Early models, such as the Drinker and Emerson respirators, were large and cumbersome but effectively provided respiratory support. The design enabled a rhythmic process of air intake and release, sustaining individuals whose respiratory muscles were paralyzed.
Its Role in Combating Polio
During polio epidemics, the iron lung became an indispensable medical tool. Poliovirus could attack the motor neurons in the spinal cord, leading to paralysis, including that of the respiratory muscles. When the diaphragm and chest muscles were affected, patients lost the ability to breathe on their own, often resulting in death.
The iron lung offered a direct solution to this paralysis by mechanically maintaining respiration. It became a common sight in hospital wards, providing a means for thousands of polio patients to survive the acute phase of the disease. For many, the device was a temporary measure, used for weeks or months until some muscle function returned.
However, for individuals with permanent respiratory paralysis, the iron lung provided long-term life support. Its widespread deployment during these epidemics cemented its place as a symbol of hope and scientific advancement against a terrifying disease. The device allowed patients to continue living when their bodies could not perform the fundamental act of breathing.
From Iron Lungs to Modern Ventilation
The iron lung’s use declined due to medical advancements. The development of the polio vaccine by Jonas Salk in 1955 dramatically reduced the disease’s incidence, making severe respiratory paralysis far less common. This reduction in polio cases lessened the overall need for iron lungs.
Simultaneously, technological progress led to the development of positive pressure ventilators, which are more versatile and less restrictive. Unlike the iron lung, which pulls air into the lungs using external negative pressure, positive pressure ventilators actively push air into the patient’s airways. These newer machines are smaller, more portable, and allow for easier patient care.
The shift to positive pressure ventilation, first widely adopted during a polio outbreak in Copenhagen in 1952, marked a new era in respiratory support. Its legacy endures as a testament to early mechanical ventilation and its impact on saving lives.