An iron lung is a type of negative pressure ventilator, a mechanical respirator which encloses most of a person's body and varies the air pressure in the enclosed space to stimulate breathing. It assists breathing when muscle control is lost, or the work of breathing exceeds the person's ability. Need for this treatment may result from diseases including polio and botulism and certain poisons (for example, barbiturates and tubocurarine).
The use of iron lungs is largely obsolete in modern medicine as more modern breathing therapies have been developed and due to the eradication of polio in most of the world.