When Dr. Philip Drinker developed the iron lung in 1928, he was responding to a terrifying new disease that was causing sudden paralysis. Doctors called it poliomyelitis — or polio. The onset of the illness was sudden, with fever followed by acute paralysis. Those who survived were, like Franklin Roosevelt, often left with crippled limbs, dependent for the rest of their lives on braces or wheelchairs. In severe cases, the lungs were paralyzed, and patients died of suffocation.

Since many victims of polio regained use of some of their muscles over time, doctors knew that if they could keep patients alive through the acute early stage of the disease, there was a chance of recovery. Drinker's machine was designed to do the work of the lungs while they were paralyzed. Vacuums connected to it worked like a huge bellows. When they sucked air out of the chamber, air flowed in through the patient's mouth and nose, filling the lungs. As the vacuum was released, the lungs fell, and the patient breathed out.

The iron lung was the first advance in treating a disease that had baffled the medical profession. Unable to determine where the disease was coming from, doctors could prescribe only quarantine and careful hygiene in the hopes of preventing its spread. Desperate families consulted faith healers, bone-crackers, and herbalists, but polio continued to cripple and kill.

Between WWI and WWII, polio epidemics struck various parts of the country seemingly at random. Severe epidemics swept the United States in the summer of 1916 and several times in the 1930s, but the most devastating epidemic occurred in 1952. In time researchers discovered an irony: polio epidemics were an unintended consequence of improved hygiene. In an era of open sewers and privies, most people were exposed to the polio virus in infancy, when paralysis rarely occurs. When living conditions improved, the disease went from being so mild that no one even knew it existed to an epidemic of mysterious origins and unknown scope.

Although polio was commonly called infantile paralysis because of its tendency to strike children, youth and adults were not immune to the disease. Iron lungs were eventually built in all sizes. The metal cylinder had "port holes" through which nurses and doctors could watch the patient's chest rise and fall with the rhythm of the vacuum pumps. Once they got used to being confined, patients reported that they found the machine comforting.

Most patients needed an iron lung for a period of weeks or months, but the lungs of some polio victims were permanently paralyzed; some people lived for years, lying prone in a metal box. One common side effect of being in an iron lung was that patients would hallucinate that they were moving, sometimes in the respirator, but more often in a car, train, or airplane. It was not unusual for patients to recall their iron lung "travels" in great detail, even after they recovered.

In the 1950s, an effective vaccine was developed for polio. The number of cases, and the need for the iron lung, plummeted. By the 1960s, patients with difficulty breathing were using a modern compact respirator. Although a few iron lungs are still in use, most have become museum pieces. As for the disease that motivated the iron lung invention, in developed nations a child is now "more likely to be struck by lightning than by polio." In 1959 there were 1,200 people using tank respirators in the United States; in 2004, there were 39.