An iron lung is a large machine that is about 7 feet (2.13 meters) long and weighs several hundred pounds. It is used to allow a person to breathe if normal muscle control has been lost or temporarily diminished. The iron lung was invented in 1929 by Dr. Phillip Drinker (1894–1972) and Louis Agassiz Shaw (1886–1940) to help victims of paralytic poliomyelitis. The iron lung is still in use on a limited basis. In the United States, 30 to 40 people still depend on the device.