The origin of this important branch of medicine lies in the effective use of positive pressure ventilation of the lungs to treat respiratory breathing failure in patients affected by poliomyelitis in an outbreak of this potentially fatal disease in Denmark in 1952. Doctors reduced mortality from 90 per cent to 40 per cent in patients receiving respiratory support with the traditional cuirass ventilator (iron lung) by using the new technique. They achieved this with a combination of manual positive-pressure ventilation provided through a tracheostomy and by looking after the patients in a specific area of the hospital, allowing the necessary staffing and equipment resources to be concentrated in one place.