iron lung

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun An airtight metal tank that encloses all of the body except the head and forces the lungs to inhale and exhale through regulated changes in air pressure.

from the GNU version of the Collaborative International Dictionary of English.

• noun A steel chamber, usually cylindrical, enclosing the entire body of a person except for the head, used to assist respiration for people suffering from disease, especially poliomyelitis. A reciprocating piston at the end causes alternating high and low pressure inside, which forces or assists the breathing of the patient within.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A pneumonic device for assisted breathing.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun respirator that produces alternations in air pressure in a chamber surrounding a patient's chest to force air into and out of the lungs thus providing artificial respiration