Iron lungs fell out of widespread use for two converging reasons: a better ventilation technique took over in the early 1950s, and polio vaccines soon eliminated the disease that had filled hospital wards with tank respirators in the first place. The shift happened remarkably fast. Within a decade of 1952, positive-pressure ventilators delivered through tubes in the airway had become the standard of care, and the enormous steel cylinders that once defined respiratory medicine were being wheeled into storage. The story is more interesting than a simple technology upgrade, though, because the iron lung was not a bad machine. It just could not keep up with the demands of modern critical care.
How the Iron Lung Worked
Before 1929, no satisfactory mechanical respirator existed. That year, Philip Drinker and Louis Shaw described their apparatus: a cylindrical tank that enclosed a patient’s entire body below the neck, leaving the head outside under normal atmospheric pressure. Air pumps (later replaced by a bellows) raised and lowered the pressure inside the tank, doing the work of breathing for the patient. When the pressure dropped below atmospheric inside the chamber, the chest wall expanded and air flowed into the lungs. When the pressure returned to normal, the lungs’ own elastic recoil pushed air back out. The device was quickly nicknamed the “iron lung,” and it supported thousands of patients during the polio era.1PubMed. A practical mechanical respirator, 1929: the “iron lung”
This approach is called negative-pressure ventilation: instead of pushing air into the lungs (which is what modern ventilators do), the iron lung pulled the chest wall outward, creating a pressure difference that drew air in naturally. The subatmospheric pressure surrounding the thorax causes the chest to expand, which decreases pressure inside the lungs and creates a gradient for air to flow in from the outside. Expiration happens passively when the external pressure returns to atmospheric, thanks to the natural elastic recoil of the lungs and chest wall.2European Respiratory Journal. Negative-pressure ventilation: is there still a role? In other words, the iron lung mimicked the body’s own breathing mechanics more closely than any positive-pressure machine does. That physiological advantage would turn out not to be enough.
Why the Iron Lung Was a Nightmare for Hospitals
An iron lung was roughly the size of a small car and weighed several hundred pounds. The patient lay flat inside the sealed tank with only their head protruding through a rubber collar at one end. Nurses and doctors could see the patient’s face, but everything below the neck was locked behind steel. Routine medical tasks that take seconds with a modern ventilator patient, like checking a wound, placing an IV, adjusting a catheter, or even bathing, required opening the tank or using awkward portholes built into the sides. Some models had sliding trays to pull the patient partially out, but doing so interrupted ventilation. For patients who could not breathe on their own at all, even brief interruptions were dangerous.
The physical bulk also limited how many patients a hospital could treat simultaneously. During major polio outbreaks, wards filled with rows of iron lungs, each one taking up an enormous footprint and requiring dedicated power. If the electricity failed, someone had to pump the bellows manually. Photographs from the 1940s and early 1950s show hospital gymnasiums converted into iron lung wards, with nurses working between tanks barely wide enough apart to squeeze through. Scaling up during an epidemic was a logistical nightmare: the machines were expensive, heavy, difficult to transport, and required dedicated staff for every patient.
For patients who needed ventilation for weeks or months, life inside the tank was psychologically brutal. They could see only what was directly above them or reflected in angled mirrors. They could not turn over, sit up, or hug their families. Some patients spent years, even decades, in iron lungs. A few individuals continued using them into the 2020s, having been dependent on the machines since childhood polio in the 1950s. The iron lung kept them alive, but the quality of that life was constrained by the technology in ways that modern ventilation simply does not impose.
The 1952 Copenhagen Epidemic Changed Everything
The pivotal moment in ventilation history came during a devastating polio epidemic in Copenhagen in 1952. Hospitals were overwhelmed with patients in respiratory failure, and the available iron lungs were not enough. A Danish anesthesiologist named Bjørn Ibsen proposed a radical alternative: instead of using negative pressure to pull air into the lungs from outside the chest, he demonstrated that positive-pressure ventilation, pushing air directly into the lungs through a tube placed in the trachea, could save the lives of polio patients.3PubMed. Bjørn Ibsen: intensive care and the conundrum of prolonging death
Ibsen’s approach had immediate practical advantages. A tracheostomy tube or endotracheal tube was far smaller and cheaper than a tank respirator. It left the patient’s body fully accessible for nursing care, surgery, and physical examination. Multiple patients could be ventilated in a single room without each one occupying a steel cylinder. During the Copenhagen epidemic, medical students were recruited to manually squeeze ventilation bags around the clock, taking shifts to keep patients alive. It was exhausting and crude, but it worked, and the mortality rate for bulbar polio patients dropped dramatically compared to what iron lungs had achieved.
The success in Copenhagen effectively brought anesthesia techniques to the general medical wards and laid the groundwork for what we now call intensive care. Within a few years, mechanical positive-pressure ventilators were developed that could automate the process, eliminating the need for someone to stand at the bedside squeezing a bag. Endotracheal intubation itself had been refined since the 1940s, when curare was introduced as a muscle relaxant during surgery and tube-based airway management became routine in operating rooms.4PubMed Central. Tracheostomy and endotracheal intubation: a short history The infrastructure and expertise for positive-pressure ventilation already existed in anesthesiology. Ibsen’s insight was to apply it outside the operating room, to patients who needed breathing support for days or weeks rather than hours.
Polio Vaccines Eliminated the Main Demand
Even if iron lungs had been perfectly convenient machines, they would have become largely obsolete for a simpler reason: the disease that filled them was eradicated in most of the world. The Salk inactivated polio vaccine (IPV) and the Sabin oral polio vaccine (OPV) brought polio under control within a remarkably short period.5PubMed Central. History of polio vaccination In the United States, the number of annual polio cases dropped from tens of thousands in the early 1950s to a handful by the mid-1960s. The last case of wild poliovirus in the U.S. was reported in 1979. Globally, polio cases have fallen by over 99% since the Global Polio Eradication Initiative launched in 1988.
Polio was the single condition that had driven mass production and deployment of iron lungs. Other diseases can cause respiratory paralysis or failure, but none created the same concentrated, epidemic-scale demand for mechanical ventilation. Once polio was no longer paralyzing hundreds of people every summer, the practical urgency behind iron lung manufacturing evaporated. Hospitals that had stockpiled the machines during the epidemic years gradually decommissioned them. Replacement parts became scarce. The expertise to maintain and operate them faded from institutional memory. By the 1970s and 1980s, iron lungs were medical museum pieces in most countries, with a few individual patients still using them at home as the last remnants of the polio era.
What Positive-Pressure Ventilation Does Better
Modern positive-pressure ventilators push air (or an oxygen-enriched gas mixture) directly into the lungs through an endotracheal tube or a tracheostomy. This approach dominates critical care today for several reasons that go beyond mere convenience.
First, the airway tube gives clinicians direct access to the lungs. They can suction out secretions, deliver nebulized medications, and sample airway fluids for infection testing. In an iron lung, the airway was unprotected. Patients who could not swallow properly because of bulbar polio were at high risk of aspirating saliva and secretions into their lungs, and the iron lung had no way to address that. Positive-pressure ventilation with a cuffed tube seals the airway and prevents aspiration, which was a major cause of death in polio patients managed with tank ventilators.
Second, positive-pressure ventilators allow precise control. Clinicians can set exact tidal volumes, breathing rates, oxygen concentrations, and pressure limits. They can adjust settings minute by minute in response to blood-gas measurements or changing lung compliance. Modern ventilators have dozens of modes tailored to different lung conditions. Iron lungs offered crude pressure adjustments and rate control, but nothing approaching this level of fine-tuning.
Third, the patient’s body is fully accessible. Surgeons can operate, nurses can reposition the patient to prevent bedsores, physical therapists can work on limbs, and family members can hold a hand without the barrier of a steel tank. This matters enormously for both clinical outcomes and human dignity during prolonged illness.
What the Iron Lung Actually Did Better
Positive-pressure ventilation is not without trade-offs, and understanding them explains why negative-pressure approaches never completely vanished. Pushing air into the lungs under pressure is not how the body was designed to breathe. The increased pressure inside the chest during inspiration compresses blood vessels and can reduce the amount of blood returning to the heart. In patients with already fragile cardiovascular systems, this can lower cardiac output and blood pressure.
Research comparing the two approaches found that iron-lung ventilation with negative end-expiratory pressure was hemodynamically similar to continuous positive-pressure ventilation in terms of cardiac output, but that a different negative-pressure approach (using a wrap applied only to the thorax and upper abdomen rather than a whole-body tank) actually produced higher cardiac output than either.6American Review of Respiratory Disease. Hemodynamic Differences between Continual Positive and Two Types of Negative Pressure Ventilation In other words, the full-body iron lung did not have a clear hemodynamic advantage over positive-pressure ventilation, but smaller, targeted negative-pressure devices might.
Positive-pressure ventilation also carries risks that iron lungs did not. Ventilator-associated pneumonia is one of the most common and dangerous complications of prolonged intubation. The tube itself provides a highway for bacteria to reach the lower airways. Barotrauma, where high pressures damage the delicate lung tissue, is another concern. And the process of intubation itself can injure the vocal cords, trachea, or esophagus. The iron lung avoided all of these problems because it never touched the airway at all. For patients who need only breathing support and whose airways are healthy, the non-invasive nature of negative pressure is genuinely appealing.7Anaesthesia. Exovent: a study of a new negative-pressure ventilatory support device in healthy adults
These advantages explain why some clinicians have continued to argue for negative-pressure approaches in specific situations, even as the iron lung itself disappeared. The concept never died. The hardware just needed to evolve.
Modern Descendants of the Iron Lung
The iron lung’s core principle, creating negative pressure around the chest to draw air into the lungs, lives on in smaller, more practical devices. The most notable modern descendant is the cuirass ventilator, essentially a rigid shell that fits over the patient’s chest and abdomen (think of it as a turtle shell connected to a pump). Biphasic cuirass ventilation can both actively pull the chest open during inspiration and actively compress it during expiration, giving clinicians more control than the old iron lung ever offered. Recent reviews have examined its use during airway surgeries, where it allows ventilation without any tube in the airway, giving surgeons an unobstructed view and workspace.8Cureus. Biphasic Cuirass Ventilation for Airway Surgeries: A Comprehensive Review
The cuirass approach has also found a niche in patients who cannot tolerate intubation or who need long-term ventilatory support at home. For conditions like muscular dystrophy, spinal cord injuries, or severe scoliosis that limits lung expansion, a cuirass can provide breathing assistance without the infection risks and discomfort of a permanent tracheostomy. These devices are a fraction of the size and weight of an iron lung, can be used in a normal bed, and leave the patient able to eat, speak, and interact normally.
COVID-19 and the Iron Lung’s Unexpected Return
During the early months of the COVID-19 pandemic, something unexpected happened: researchers started looking at negative-pressure ventilation again. The reason was straightforward. Hospitals worldwide were running out of conventional positive-pressure ventilators, and manufacturing new ones fast enough was impossible. The crisis prompted investigation into ventilators that were lower in cost and offered fewer health complications.9PubMed Central. Investigating the effect of materials and structures for negative pressure ventilators suitable for pandemic situation
One notable project was the Exovent, a lightweight, torso-only negative-pressure ventilatory support system designed by a team of engineers, doctors, and nurses in the United Kingdom. Unlike the old iron lung, the Exovent did not enclose the whole body. It covered only the torso, was made from modern lightweight materials, and was designed to be simple enough to manufacture rapidly during a supply crisis. Testing in healthy adult volunteers assessed its comfort, nursing acceptability, and ability to support breathing.7Anaesthesia. Exovent: a study of a new negative-pressure ventilatory support device in healthy adults The Exovent and similar prototypes were not designed to replace ICU ventilators for the sickest patients. The idea was to provide breathing support for patients who were struggling but not yet critically ill, potentially keeping them off invasive ventilators altogether.
The pandemic also reframed a longstanding clinical observation: many COVID-19 patients who were placed on invasive positive-pressure ventilators did poorly, in part because of the lung-damage risks that come with pushing air into already inflamed tissue. Some clinicians experimented with prone positioning (having patients lie face-down) and non-invasive breathing support before resorting to intubation. In that context, the gentler mechanics of negative-pressure ventilation seemed worth revisiting. Whether any of these pandemic-era prototypes will enter mainstream clinical use remains to be seen, but the episode showed that the iron lung’s underlying principle is not as obsolete as people assumed.
The Few People Who Never Stopped Using Iron Lungs
While hospitals moved on decades ago, a small number of individuals continued to depend on original iron lungs for their survival well into the 21st century. These were people who contracted polio as children in the late 1940s or early 1950s, before vaccines were available, and whose respiratory muscles never recovered. Some used the iron lung only at night, relying on residual diaphragm function during the day. Others needed it continuously.
Keeping these machines running became its own saga. Manufacturers stopped making iron lungs in the 1960s. Replacement parts had to be fabricated by hand or scavenged from decommissioned units. A small network of volunteers and repair technicians, some of them retired engineers, kept the machines functional through improvisation. When rubber gaskets cracked or motors burned out, there was no catalog to order from. The patients themselves often became experts in the mechanics of their own machines out of necessity.
The experience of these last iron lung users highlights something that gets lost in the narrative of medical progress: for the specific problem of breathing support without airway invasion, the iron lung worked. It was reliable, mechanically simple, and avoided the infection risks of intubation. Its disappearance was driven less by the machine’s failure than by the disease’s disappearance and the healthcare system’s reorganization around positive-pressure technology. Hospitals invested in ventilator infrastructure, trained staff in intubation and tube management, and built ICUs around the positive-pressure model. Once that ecosystem was in place, there was no institutional path back to negative pressure even for patients who might have benefited from it. The iron lung did not lose a fair competition on clinical merits alone. It lost because the world changed around it.