iron lung

iron lung, mechanical medical device, sufficiently large to enclose most of an individual’s body, used to maintain respiration in persons who are unable to breathe on their own. An iron lung, the main portion of which consists of a horizontal metal cylinder, essentially acts as a mechanical respirator, wherein a bellows positioned at the foot end of the machine moves in and out to produce changes in pressure that stimulate breathing. Historically, the iron lung was used for patients affected by paralysis caused by polio; many such patients were unable to breathe on their own. After the early 1950s, following the introduction of the polio vaccine, use of the iron lung declined, such that today it is generally considered obsolete.

The first iron lung was invented in 1927 by Philip Drinker and Louis Agassiz Shaw at Harvard University; it was implemented with patients in 1929. The machine, known as the Drinker respirator, consisted of an airtight chamber that enclosed the body, with bellows attached at the foot end and a rubber seal at the opposite end to prevent air leakage around the patient’s neck. The Drinker respirator was used to treat patients with paralytic polio and individuals who were unable to breathe as a result of coal gas poisoning and similar conditions. In 1931 another version of the machine, which included features such as a leather bellows to help silence the machine and portholes through which doctors could access the patient for medical procedures, was invented by John Haven Emerson. The so-called Emerson respirator became increasingly common in hospitals and other medical facilities beginning in the late 1930s.

In the iron lung, the patient lies on their back with the body inside the chamber and the head and neck resting on a stand outside the chamber. The movement of the diaphragm of the iron lung is the primary mechanism by which the machine aids respiration. Its movement one direction pulls air out of the chamber, producing negative pressure and allowing fresh air to be drawn in. This mechanism is similar to the way in which contraction of the diaphragm muscle in the human body lowers internal pressure in the lungs, thus expanding the thoracic cavity and causing inspiration of air. As the diaphragm of the iron lung then moves in the opposite direction, mimicking relaxation of the human diaphragm muscle, positive pressure is produced, causing the patient’s lungs to contract and push air out.

Use of the iron lung typically was limited to a few weeks or months, depending on the severity of the patient’s condition. For many patients, the iron lung was used alongside physical therapy, and some patients used the machine only at night or for only a few hours of the day. In a few instances, however, patients spent their entire lives in an iron lung. One such person was Paul Alexander, who lived in an iron lung after developing paralytic polio in 1952, when he was six years old. Alexander was unable to leave the chamber for more than a short period of time every day. Nonetheless, he attended law school and started his own law practice; he died in 2024.