An iron lung is a large, horizontal metal cylinder designed to support breathing in individuals with paralyzed respiratory muscles. This mechanical respirator encloses the patient’s entire body except for their head, providing life-sustaining ventilation.
How the Iron Lung Functions
The iron lung operates on the principle of negative pressure ventilation, mimicking the body’s natural breathing mechanism. The patient’s body is sealed within the airtight cylinder, with a rubber collar ensuring a tight seal around the neck. A pump or bellows mechanism then alternately decreases and increases the air pressure inside the chamber.
For inhalation, air is pumped out, creating negative pressure around the patient’s chest. This causes the chest wall to expand, drawing air into the lungs. For exhalation, pressure inside the cylinder increases or equalizes, allowing the chest and lungs to passively recoil and expel air. The rhythmic cycling of pressure within the chamber effectively forces air into and out of the lungs, compensating for paralyzed or weakened respiratory muscles.
Its Role in Medical History
The iron lung gained recognition for its role during the polio epidemics of the mid-20th century. Developed by Philip Drinker and Louis Shaw in 1928, it was initially used for conditions like coal gas poisoning, but gained prominence with poliomyelitis cases. Polio, a viral infection, could lead to paralysis of respiratory muscles, making independent breathing impossible for many patients.
Hospital wards in the 1940s and 1950s often featured rows of these large metal devices, providing life support for children and adults afflicted with the disease. The iron lung became a primary method for treating “paralytic breathing failures” associated with severe polio, often being the only means of survival for those with respiratory paralysis.
Many patients required the iron lung for weeks or months to recover. Some with permanent chest muscle paralysis relied on it for a lifetime. The device provided a bridge until patients could potentially regain respiratory function.
The Shift Away from Iron Lungs
The widespread use of the iron lung began to decline significantly following two major advancements in medicine. A primary advancement was the development and widespread distribution of the polio vaccine in the mid-1950s. This vaccine dramatically reduced poliomyelitis incidence, virtually eradicating new cases globally. With fewer new cases of polio causing respiratory paralysis, the need for the iron lung diminished substantially.
Technological advancements also led to newer, more versatile respiratory support devices. These modern ventilators offered advantages in terms of patient accessibility and overall management. By the 1960s, these alternative methods began to replace the bulky iron lung in standard medical practice. The last iron lungs were manufactured in 1970, marking the end of an era for this once-prevalent medical device.
Modern Respiratory Support
Modern respiratory support systems primarily utilize positive pressure ventilation, a fundamentally different principle than the iron lung. Instead of creating a vacuum around the body, these ventilators actively push air into the patient’s lungs. This is typically achieved through an endotracheal tube inserted into the windpipe or a mask fitted over the patient’s face.
Positive pressure ventilators, such as mechanical ventilators, inflate the lungs by delivering a controlled volume of air and oxygen under pressure. They offer greater flexibility in adjusting breathing parameters and allow easier access for patient care. These devices are compact and can support a wider range of lung conditions beyond just muscle paralysis.
While positive pressure ventilation became the standard, some newer negative pressure ventilation devices, like the cuirass ventilator, also exist. These smaller units enclose only the chest or torso, providing some of the benefits of negative pressure while offering more mobility than the full iron lung.