An iron lung, more properly known as a negative pressure ventilator, is a medical device which is designed to help patients breathe when they have difficulty doing so on their own. It has been largely replaced with positive pressure ventilators, due to the fact that it is extremely unwieldy and difficult to use, although a handful of individuals continue to use iron lungs, and they are employed in some forms of non-invasive therapy to treat people with paralysis and breathing conditions.
The iron lung is probably most closely associated in the mind of the public with poliomyelitis, also known simply as polio, a debilitating disease which causes paralysis in some patients. At one time, polio was a scourge throughout much of the world, until vaccines were developed in the 1950s, and the iron lung was a crucial treatment tool for people paralyzed by polio. For patients with temporary paralysis, the negative pressure ventilator would help them breathe while they recovered, and patients with permanent paralysis might be confined to the device for the rest of their lives.
The iron lung consists of a long chamber, classically built from steel, although other materials may be used as well. The body of the patient is placed inside the chamber, while his or her head projects through a flap to the outside. When the chamber is sealed, the pressure inside can be regulated with pumps. When the pressure in the device falls below a certain point, the lungs automatically inflate in response, sucking in air from the outside, and as the pressure rises, the lungs deflate.
Versions of the iron lung were developed as early as the 1800s, but the first functional and easily produced one was developed in 1927 by Philip Drinker. These quickly filled hospital wards all over the world, and inspired a number of refinements to make them easier to build and handle. While iron lungs are no longer produced today, some museums with collections of antique medical equipment have one on display, sometimes with accompanying material written by people who lived or spent time in them.
For the patient, life inside an iron lung is highly confined, ensuring that the patient requires a lifetime of care. The development of functional positive pressure ventilators made a huge difference in the lives of many polio patients, allowing them to be much more mobile and functional, as these ventilators rely on a tube inserted into the lungs to inflate and deflate the lungs.